Very roughly Dex,
The big question is how much loss in your room happens from one meter to whatever you listening distance actually is. You can find that out (for the most part) by using an SPL meter, measuring tape and some test tones or sweeps. In room sensitivity depends on your room--how absorbant or reflective it is, smaller rooms are more reflective than larger rooms, how close your speakers are to the walls or corners--lunar phase and if you are holding your mouth right. OK, the last two won't happen but you get the idea.
Say you want to test it--to know what happens just because--it is an audio OCD thing so this is how you do it (roughly, for the most part, generally speaking yada, yada, yada....aim away from face) Take your SPL meter or phone with SPL app and put it on a stand (tripod, 2x4 etc.) and measure out one meter or 39.4 inches and get your reading at say 1 KHz test tone. You don't need to blast the speakers but it needs to be loud enough to prevent the AC unit, fans or background noises from screwing up your readings. Say 80dB would be good. Once you get a good reading of say 80dB at one meter--then move your meter/phone back to where your ears are located and don't mess with the volume. If you get a reading of say 72dB, then subtract that from 80dB at one meter for your loss over distance or 8dB. You can also do sweeps from 400 Hz to 3,000 Hz or whatever you like just because you can.
EDIT Do not hold the sound level meter in your hand with your body behind it. The sound will reflect off your body and throw the reading off--generally a higher SPL than actual. This is why it is a good idea to use a tripod, stick, piece of wood or rod to hold it in position. Don't want reflections of the thing holding the meter to make a mess of things. Learned that one the hard way...
Now that you know the loss, then you can calculate back to one meter with simple math. Just add your loss to the maximum SPL you want--for fun say it is THX reference level of 105dB at your seated distance. Subtract the 8dB loss (or whatever you read) to the sensitivity/efficiency of the speaker--or 92dB in your case to make 84dB at one watt/one meter (or 2.83V one meter) Change watts to dB/W so you need 21dB of gain to get 105dB at your seated position which is around 128 watts peak. Generally speaking (if you hold your mouth right) Dolby recommends 3dB of headroom over your peak wattage demands so around 250 watts just to be "safe". If you want 100dB peaks with your speakers (each channel, not together) that would demand 5dB/W less so instead of 128 watts, you would need only 40 watts. Do the Dolby 3dB of headroom thing, that would be 80 watts just to be safe.
This is why it is so hard to throw a standard wattage out there--depends on the room, your seating distance and the efficiency of the speakers. Say you have 87dB speakers that can handle 200 watts (for instance) your dB loss is 8dB and you desire 105dB peaks for THX reference. This means you are starting at 79dB due to lower speaker efficiency and would require 26dB of gain--400 watts of power. Throw in the desireable amount of headroom to make that 800 watts
and if you ever clip the amp from drinking a few too many, you might wake up the next day with blown speaker drivers. The speakers are rated at most of 200 watts--not a good idea to run 400 or 800 watts into them--at least not using highly compressed EDM and really putting the screws to them. For this reason, for that useage--I'd go with higher efficiency speakers as each 3dB gain in efficiency nets power demands cut in half.
Back in my mis-spent youth, I had two systems--the "A speakers" were small, very good sounding bookshelfs with subwoofer at 87dB efficiency but would start to distort at around 60 watts of input which is around 105dB at one meter. My "loss" due to distance was around 7dB so I could get around 98dB at my seated distance without sound quality dropping off too much. What I did was add my "B speakers" which were PA speakers at 100dB one watt/one meter and they handled 350 watts without issues. My gain of +13dB of efficiency AND +7dB of power handling gave me 20dB more output--including ringing of the ears and visits from law enforcement. I would listen to the low efficiency bookshelf/sub system for sound quality at lower levels and kick i the PA beast speakers when going into rock star mode--keep drinking until it sounds good!
After that educational experience, I did strive to get the smooth and clean response of the bookshelf/sub system with the efficiency of the PA system in one. I can do that but I lose the small bookshelf size immediately--to make the main speakers smaller, I threw away deep bass response and let the subs take care of that. My mains are 20"H X 12.5"W X 12.7"D (51 cm H X 31cm W X 32cm D) and weigh 36 pounds (16.3 KG) Not exactly small but manageable--and at 98dB one watt/one meter I have no problems with THX reference levels at 3 to 4 meters on 100 WPC AVR power. It would be fun to have something like JBL 4722N movie theater speakers at 104dB, I'd use 75% less power but the size/weight of the things would get my idiot butt thrown out of the house--but it would be fun to play with. Of course, getting enough subs to "keep up" with the 4722N would get huge, multiple subs and some dedicated electrical lines to feed monster amplifiers but a guy can dream!
If you ever find a speaker that can punch out 100dB at one watt/one meter while being less than 10 KG of weight and less than 30 liters in side--let me know!
It could happen, maybe an 8 inch mid-woofer with graphene construction along with one of those horn loaded Beyma AMTs (102dB one watt/one meter) might make it to 80Hz on the low end while giving massive efficiency to match the AMT. Cost? Well... you really have to pay to play when dealing with neodymium motors and I'm sure once graphene hits the scene--just the parts will run easily 4 figures Euro/$ or pounds. Alas, that is just the parts, the crossover filters, box, grills, input terminals etc. are extra. No, graphene is not available in speakers yet--give it some years and it might become available--eventually.
I call it the built in approval from my spouse, she won't complain (much) if I can get the same efficiency with a speaker half the size--at least I have that going for me. Now I wait--and wait--hope I live long enough.
In summation, use the SPL measuring at 1 KHz or whatever to determine the actual loss in your room at your preferred seating distance. Write it on the bottom of one of your speakers if you have to...but it is a good number to know when doing rough calculations of what power or speaker efficiency requirements you need when/iff you do upgrades in the future. Always good to have a rough idea of what you need before you start burning up the bank account. My wife actually trusts my calculations now, at least I have her fooled.
My LCR is done, now to build some new surrounds to replace the older, less efficient ones so I can go into rock star mode in Atmos--just because.
Glad my babble helped you out--sure beats having 5 sets of speakers laying around to figure out what works. Life is too short to be throwing speakers all over your room and shipping is a serious time sucker that can be better used doing something (almost anything) else. Have a great day and keep it between the curbs.