I use an ARC VT100 MKIII w/my Genesis 500's and they sound superb. You only need one, no need to biamp. You can find one used for well within your price range. I think two would be overkill!
Tube amp for Genesis 500
I am considering going to tube amps for my Genesis 500. They are the front speakers for my home theatre and are presently powered by a Pass Labs X5 (250W x 4ohm)and run thru a Krell Showcase processor,but I want the tube amps for more musical stereo listening. Due to space considerations I would like a stereo/dual mono version with enclosure/cage for pet protection. Budget - 5K. Also, what are the pros/cons of self biasing? Any present/previous Gen 500 owners out there who can lend their expertise?