I went down to NFM and listened to the SVS PB-2000, 4000, and the R-115SW. The PB-2000 was no where close to filling the room like the R-115SW. The 4000 had more low end oomph for sure, but at $2K, it was way more than I wanted to spend. I went with the R-115SW, and it sounds great. It seems to crush the KSW-15 in every way I can hear. I can hear notes in bass lines with it that the KSW-15 muddled. So far so good!