I don't think you would need an external amp of any size in the room. 7' from the screen means 7-8' from the speakers. No matter what speakers you get you won't need more than what your AVR can deliver to hit ear splitting levels, e.g. "reference".
If this is strictly for HT use Klipsch would be a good choice, dynamic, bright, kind of theater like and fits your budget.
But in such a small room nearly any decent speaker would work. I use 5 NHT SuperZeros driven by a 50watt/channel AVR in a 13x14x9 room and have yet to run it at 0db during blu-ray movies. I can get in the mid 90dbs at the LP which is pretty loud for a long action movie.
What sub are you using or planning to use?
Klipsch RF-62II, RC-500, RS-400, SVS PC12+,
Def Tech SC8000
Harman Kardon AVR 1600
PS3, Apple TV, Sharp 70" Qattron