With a $300-400 budget looking to fill a room that large with a HITB avr pushing them?, I think the OP is screaming for a pr of Klipsch...but even then, he needs another $200 or so bucks to do the room justice with reasonable SQ.
Most people are not overly concerned about flat frequency response, driver accuracy, etc, they just want the music to sound like what they've heard on radio, in the car etc. But, to do this right, I think the OP needs to tack some more money onto the budget, even if it means waiting.