I have owned an SVS SB2000 for a couple of years and am very happy with it. It's on my main living room 5.1 system which is really used 95% of the time for 2.1 channel music. The SB2000 is the improved version of the SB12-NSD.
A couple of months ago I picked up a pair of LS50's for my desktop office system and wanted a sub to supplement them. The LS50's go lower than they should for a little 5-1/4" driver, but there's just no argument that a sub is need for a lot of today's music. (I'm not stuck in classic rock like many of my peers.)
On my "KEF Enthusiasts" Facebook page there was a member selling off a new KEF Kube 10b that didn't work out for his space, at about $150 off list price. I snapped it up, thinking it would be just right for my office setup. I figured it wouldn't dig as deep as my SB2000, which I tried in the office, but that would be OK because where I have it in the corner it's DSP settings would help. I get a lot of room gain and figured it would cover 90% of what I listen to.
Well I was mistaken. The Kube 10b shocks me with what it does! I had little faith because historically KEF used lower power amps and smaller drivers in their subs, making them under-performers as compared to internet-direct subwoofer makers like SVS, Rythmik, Hsu Research, and others. Boy was I wrong on the Kube 10b!
This sub is noticeably faster-acting, tighter bass than the SB2000 and just sounds GREAT! Hard to describe, but as good as the SB2000 is this Kube 10b continues to surprise me. No, it can't shake the whole room like the SB2000 can (I'm in a second floor with a rent-paying tenant below me), but what it does do for music is just blend so perfectly seamless with the LS50's that I often have people sitting in my chair to audition my system ask me how those LS50's put out that much bass. The more-educated ones do start looking for the sub, but hardly notice it sitting over there in the corner off to the left.
I always avoided subs made by major, popular speaker makers because they were never much of a value in view of what the internet direct sellers were selling. I'd heard many a Definitive Technology, B&W, KEF, Martin Logan, Paradigm and other subs from their lower-priced speaker lines and was unimpressed. All the changed with the KEF Kube 8b, 10b and 12b. Yeah, they're still priced a little high at list price, but any 10% discount and they jump ahead. I'm very, very happy with mine.