See if we are on the same page,
Since you are a flat pack/pre-assembled crossover kind of guy--I am assuming you are not talking about learning speaker design, selecting drivers to match your desired design, modeling/building/tweaking passive crossovers and so on. Just something "to get your feet wet" I guess? If so, I would strongly (with heavy foot stomping!) suggest building a subwoofer or maybe start off with a pair of surrounds. Subwoofers are great, learn the software, play around with different box sizes, different tunings of the port (or passive radiator etc.) get to know port resonances, air speed through the port and what all that means in software. Once all that is in balance, then build the thing without worries about crossovers, phase issues, cone breakup, off-axis response and all that other madness. A great introduction to speaker building and the drivers tend to be quite durable to mistakes, box leaks, porting screw ups and all those other speaker gremlins. You can build one, measure it to see if it matches your software simulation, play around with adjustable electronic crossover points and so on.
I would start off with something like a 12/15/18 inch subwoofer depending on size/weight/complexity/cost and have fun with it. You are doing this correctly, you have time so that allows for the learning process without a time limit that drives you to make errors. For me, I'd start with something like a 12" sub in a 4 cubic foot box ported to around 18 to 22 Hz depending on driver and have fun with it. Keep the port "external" with the PVC pipe sticking out so you can play around with different porting to see/hear how it measures OUTSIDE then take it inside to see how the measurements change in different rooms.
After building a sub, then you can wade out into the ocean a bit deeper--realistically determine what your "forever home" room size will be, the distances of the surrounds and finalize what SPL level is required or desired. You can start with something inexpenisve, very easy to build and small... say a Volt 6 or Volt 8 surround speaker. Get the flatpacks, maybe try your hand at soldering. The Volts come with the board in the kit so a great opportunity to learn to solder. You can find soldering tutorials on Youtube and I'd advise to start soldering wire first, get the hang of it so it becomes second nature. Then solder in the components using heat sinks to keep the components cool and don't forget solder paste! It is not hard to solder, even a ten thumbed village idiot like me can do it.
After completing your first sub and a pair of surrounds--listen to the end result. Does it sound good to you? Does it measure well? Run your first built system for awhile, learn to critically evaluate the system and be hard on yourself. Play around with the adjustments or room correction on the AVR, get used to using those adjustments with the simple 2.1 system--have fun with it! Maybe then take the thing apart and try out a different finish, maybe veneers or putting a nice table top on the sub to "stealth" it out. This will get you over "the honeymoon phase" of everything is great because, human nature dictates everything rocks when you built it!
Once you get to the point of your new home, then you'll have a working knowledge of what is required to fill your new space. You also know full well of what time/size/cost of any designs you are looking at. To help prevent any issues with you wife when it comes to your new hobby, it is best to mock up the size of the new speakers or subs with cardboard boxes. Seriously, a cardboard box in the suggested size before you build a bunch of coffins or subs the size of dumpsters really give an accurate visual of your decent into madness. You can "win over" your wife by including her into what finish or color she wants to match the room. Grills don't have to be black...you can go with different colors to match the walls or stealth them all the way to getting pictures printed on the grills if you like. You built it, no reason to make them look like the Best Buy speaker room. My wife went for black speakers with magnetic grills with grey acoustic cloth--sort of an accent color to break up the imposing darkness of the speakers. Pretty grills go a long way to calming the nerves of others that don't want the room to look like a coffin showroom at the local funeral parlor.
Once you get good at building grills, it is easy to change out the acoustic cloth to something else when/if the style of the room changes.
Another thing that works well is speaker size. If your wife wants something the size of a tea cup which won't work well for performance, throw AVS under the bus and show her pictures of far more insane setups than what you are proposing. If you want HTM-8's for your left/center/right and Volt 6 for surrounds--show her rooms with HTM-12's with Volt 10 for surrounds! If you want HTM-12s...show her Titan 615's or 1899's so your proposal seems more "sane". If you just have to go with Titan 615's, there is always images of the system pictures of BassThatHz uses--he has 29 subwoofers which will make whatever you want look positively small in comparison.
Be careful though, she might just divorce you if you push it too far, too fast.
I summation, I would start by building my own subwoofer first. It is the easiest way to learn, won't cost you a fortune and will give an indication of how deep you want to go into the pool. If your results end up being so ugly it would get throw out of a modern art show--there is always a use for an ugly garage sub!
Ugly DIY projects have a home in the garage--they are supposed to be ugly according to the latest documentation on man cave style. The first sub build should be about performance only, as long as the box don't leak it is a win. You can practice on it with veneers, duratex, paint or carpet if you like. Once you get past the level of a high school car sub--then you can tackle your first surrounds with the flatpacks. A nice, small box to learn various ways to finish them, play with small grills and if that project ends without your wife protesting--then you can have the skills needed for the "real" speakers and subs once you move into your new house.
Good luck, enjoy the build and you can never have enough clamps.