I know this is late, but here's hoping your still reading. I have used similar subs strictly as a center channel only sub (both down to just 40Hz) before being turned over to a real sub (SVS PB12 NSD/2) I have DefTech BP7001sc as my mains and a LCR2002 center and noticed the center could never handle the deep bass that the mains had (but knew that it wouldnt either) I have my mains crossed at 40Hz also.
One day a few months back, I came across the Audiosource AST10 sub (which is similar to the PSW110 (almost exactly) except the PSW110 has a larger enclosure. Anyway it gave decent bass being used as a mid bass driver, but to keep up with my mains, it had to be set at maximum gain to just try and keep up, but even at 10 the sound was stiil decent (not great mind you, but gave me more bass than the center by itself). Then two weeks ago I came across a DT Prosub 800 (update from the Prosub 80) and this sub trounced the Audiosource sub. It had way more punch, delved deeper and I only had to have the sub halfway up to keep up with my BP7001s.
My suggestion buy the DT sub, but be warned it is only good to about 38 Hz before it drops, it's -3b mark is at 32Hz and -6db is at 28Hz, so it should not be used as a full range sub, but would make a great mid bass sub or as I did to help out speakers that can't get down into the 40Hz range before being passed on to a real good sub, like SVS, Hsu or ED.
I hope the OP is catching this, I just didn't see this thread till today.
btw I spent 80.00 at a pawnshop for the Audiosource sub and 200.00 for a brand new Prosub 800 (Ultimate was having an overstock sale)