You can get a used HK Signature 2.1 110x5 amp for ~ $400 ---- use four channels to passively biamp the 2.5i mains (to get more juice and SPL) and the 5th channel to drive an NHT Audiocenter1 center.
You should still get a powered subwoofer for the dedicated LFE channel. Lots of good choices. For under $300 new, this 10inch Dayton (only $125) gets alot of praise:
http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=300-632&DID=7
You should still get a powered subwoofer for the dedicated LFE channel. Lots of good choices. For under $300 new, this 10inch Dayton (only $125) gets alot of praise:
http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=300-632&DID=7