Quickly, used is good, just talk to the guy with the used equipment - on the phone - first. Many of these guys are particular as well as audio enthusiasts, who are simply upgrading to even more expensive equipment. They usually have good stuff for sale, but a few people do not.
Your room is sized nicely, but is not too large. One 12" sub should be sufficient. Or 10", until you can upgrade.
In the short term, for a receiver I like the Denon stuff and the Pioneer Elite; if you can find a good example used it is hard to go wrong with the newer Elite receivers. Anything over 70 wpc will be good, as long as you get a high quality receiver with a large power supply! That's why I like Denon and the Elite series, 70 wpc actually means 70 wpc. With several other mfrs 110 wpc means 60... Another story, explained in the thread linked to below...
I'm sure there are more, but I know of three options for inexpensive speaker systems that have a chance of delivering good sound. If you want big
crappy sounding speakers, these are not for you!
Paragigm CT110, Energy act6, and Mirage Nanosat all list for around $800. Gallo
might have a small system that would fit into this category too.With any of these systems, you shouldn't expect audiophile quality sound at really loud volumes - but you should expect music and dialoge that is accurate and pleasing to the ears.
The sub you get with these systems will round out the audio spectrum, but not have you holding your chest from the impact the top fuel dragster on your television screen is providing. (But, to do that
, you need a $1000 sub...)
You might think of this as a two-stage operation, where will you start and where do you want to wind up? One option is to start with one of the three/four quality mfrs. I suggested, with the idea of trading up when you can. That is the only way, in my opinion, you will reach your goal (assuming good, accurate sound is your goal). If you try and do it all at once: for $1200 you can do small and pleasing, or big and crappy. Being lucky and prudent and finding good, used equipment will get you closer to big and good, for the same money, sooner.
I'm saying $2000 to $2500 for an excellent bottom-rung Really Good system. For good (?) information on options for a pretty good system,HERE IS a well thought-out (?) post
I did for someone else who had a room with volume a little larger than yours.
Hope this helps!