SVS, RSL, and Hsu are all solid options. Monoprice Monolith is great too. The customer service for Monoprice isn't bad, but its more like a typical large corproation than the personal service that you get with these smaller companies. I think you have already identified the best bang-for-the-buck subs in terms of performance. I think the RSL sub would dig the deepest, but the Hsu sub would hit the hardest, and the SVS and Monolith subs would be somewhere inbetween. There isn't a bad choice between them.