I had a hard time talking my wife into letting me put a box bigger then an end table in our living room. For some reason she did not mind the cylinder models of SVS. It hides away very nicely in the corner and produces gobs of sofa shaking bass. I have never felt it to be muddy or sloppy at higher SPL levels. It has always been tight and quick. We primarily use it for HT, but once it a while I will listen to music... letting it fill in the low end. I am never left wanting.
I have a SVS PC+ 20-39 with the 550 watt Bash amp. I upgraded to the later 12.3 driver, they have a 12.4 out now. I am not sure I notice a huge difference between the old driver and new... but it was a cheap upgrade so I did it.
If I was to do it all over again... I think I would choose a cylinder again, just because of the way it fits in my room so well. If I had to choose I would do the Ultra 13 cylinder in a heartbeat. Actually because of the size of my room I would love to have TWO!!!!!
Rayo