If you go to the forums page on AVTalk.com and HTshack.com, you'll see a link for subwoofer tests. There, you'll find threads with results for many different SVS models, as well as their competition. Based on these results, the SVS PB series clearly represent great performance for the $, while the Ultra series could claim performance as good as anything at any price (arguably better than anything at any price, depending on your priorities).
For HT use, either of the SVS lines are probably unbeatable at their price point. (In your sized room, the PB should be wonderful, the Ultra even better - "tighter, louder and cleaner" if you can tolerate the SPLs needed to experience that!) For music only use, you can make a case for the Rythmik subs (which I chose), but that's a matter of trade-offs. Either way, you might want to look at the test results in order to make a more informed choice.
God Luck
Marty
