3 channel amp for H/T

I am looking to add a 3 channel amplifier to my home theater.  The room is quite large, and it seems to get a strong viewing experience, I am having to crank the volume quite a bit.  Current setup is as follows :

Yamaha RX-V1600

Paradigm CC-270 Center Channel

Paradigm Monitor 7 v.3 Fronts

B&W in wall rear channels

Martin Logan Dynamo Sub

My thought is to push more power through the fronts/center, while utilizing the Yamaha on the rears.  Not looking to break the bank (sub $1K for an amp), and am open to used equipment.