I've got a B+W ASW 675. For the most part it's excellent, but as a bass fiend I sometimes find it lacking in outright extension and find that I come up against its limits when I push it hard. For all B+W's top-notch engineering, I find myself reminded that it is a small driver in a small box driven by a big amp and clever EQ. I tried the D.I.Y route with a CV Stroker 18" driver in massive MDF box, driven by a buttkicker 1000w amp but I didn't like the sound. I've read a lot about SVS subs on these pages, I'm very interested in the PC-ultra 16-46. I listen to A LOT of music on my system. I've also considered a second 675, a 750, and also the bigger REL subs even though I can't afford them. Would any sage minds out there care to give me your thoughts?