The SVS WILL crush the B&W.
My PC+ 20-39 is very compareable to the N800 sub... So the PB12-ISD would easily play lower, better, and not have the "boominess" of the B&W.
I went through the B&W 600, 650, 675, 800, and 850 before I settled on the SVS...and it by far has impressed me far more (for the price) than any of the B&W subs. I love my B&Ws, don't get me wrong, I want my 802Ds (if only I could afford them)!!!!! But their subs leave something to be desired.
I agree with Eric Ha as well, the PB10-ISD would definitely give the SVS 600 a beatdown. The B&W 600 sticks out like a sore thumb, it's more heard than felt. It does not integrate seemlessly into the soundstage. My friend's B&W 600 I can point it out every time exactly where the sub is. I had my SVS over there, you couldn't tell if it was on at all, it seemed like the mains were play just that incredibly low...

That's how I like it.