Parts express Titanic 10" sealed sub is what I have had for 10 years fed through line level out from my preamp. Blends very well with my MMGs. $400 kit or $580 assembled. The kit is easy.
http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-760
http://www.parts-express.com/pe/showdetl.cfm?partnumber=300-760