I've got an older MTX 801d pushing my single 12" 8500 series sub and it sounds pretty good. I've also got an MTX TC6001 that has barely been used at all that I would sell or trade for a nice 2 channel amp. The 6001 is 600 watts rms at 2ohm's and is underated so it actually does a little more than that. Here's a link to it,
http://www.mtx.com/caraudio/products/amplifiers/TC6001.cfm
Is your sub the single voice coil or the dual voice coil one??