Probably can get a 3B-ST for that, but a 4B-ST may be a tougher find. McCormack and Aragon both good choices too. I've done both passive bi-amping (4x100W) and bridging (2x300W) with a Citation 5.1 , or consider the 7.1 (4x150W or 2x450W, all at 8 ohms but stable well below 4) ... should be available for less than $700 and $1000, respectively. Very high value IMO.
