What is your budget? FWIW, I have had an old PF15 (by Def Tech) sub since 1994. It has been reliable, but kinda boomy. Perhaps the supercube is better, but for the money, there are many popular alternatives among audiophiles. Check out SVS, Hsu, Outlaw Audio, AV123.com, REL, James, and others for subs that are favored by audiophiles. In general, we look for subs that are less boomy, more accurate, "quick" - meaning less overhang and bloat, have good low end extension, and the ability to blend well with your mains. This last point is crucial to good, coherent sound. I bought a couple of Vandersteen 2Wq subs used here on Audiogon, and could not be happier. Easily the best part of my rig. The Def Tech is now used only for the LFE channel when I watch films.
