I only have a 2.1 system in my bedroom which is of similar size to your room. I have the M22's powered only by a Rotel RA-01 40w amp and it sounds fantastic. I've not heard the M2i's, but for me, I don't think I would be happy going for anything less except for maybe the M3's. I should mention though that the M3's are supposedly more laid back sounding than the M22's or the M2i's. I've not heard them either, but I believe all the fanatastic reviews speak for themselves.
You should be fine with the sub, but if you're looking to save money, this is where I would look elsewhere (am I allowed to suggest such thing here?). I've got an 8" Yamaha YST-SW215 (120W) which was less than half the price of the EP 125, and it works out great. Look for reviews online for it. Better yet, if you've got a Best Buy in your area, then check it out.
Let's pretend for right now that you are not going to be listening to DVD-Audio or SACD discs!
You will need a lot of cables for that purpose! But if it's just a DVD player or a cd player, then all you would need is simply a digital optical (or digital coax)cable and you should be set! Oh yeah, and also a subwoofer cable!
I almost forgot about video cables...What kind of TV are you going to use?
