What is the forums opinion of SVS subs?

+1 for sure on the isolation feet and plus however many on the SVS. I use SVS SB4000,SB3000 and PC2000 ULTRA with fantastic results. After 40 years of trying this combo is unmatchable in my room.

I have an SVS and a B&W. Love the SVS much cleaner than the B&W, deeper bass and great value for the money. Overall great sub! Good luck with your pick.

@ratboysr, I may be wrong but I get the impression you think it necessary to have all subs in a multi-sub set up exactly same model. You are free to use a different type and in fact may prove beneficial. For example when helping a friend with 3 subs, 2 of them 10" and 3rd 12" my measurement showed a stubborn partial null at about 70Hz. Floor space was a bit lacking so I brought over a 6.5" little sub in a 9" sealed cube. After some experimentation found it worked wonders placed about 4ft off the floor on a large bookshelf.  Measurement confirmed the the null had improved from -10dB to -4db.  The small sub was about 5ft away at almost ear height so would not need much power but received enough to further smooth out the room response. In fact when turning up the volume on this sub I could fill in that 70Hz completely but raised a nearby peak a couple of dB. I erred on the side of caution to protect the 6.5' driver.

Generally it is best, for easier integration, to stay with sealed boxes. Multi - subs are transformative and I am constantly surprised by the reluctance to accept/ embrace the concept.

If you are considering the SVS line another brand that gets little attention but are as good or better than SVS is Arendal Sound for the same money. The 1723 series subs are very good. 

My experience is with a Plus and an Ultra, both 8-10 years old:

The main issue was the volume control, which blasted when barely cracked. I trained many different methods to employ them, to no avail. I had them with 3 different speakers. It took years of advertising them FS until someone bought them for his Video system, which is what the company originally was based on. So, if you're looking to use them in a  channel system ask before you buy

hth