That ULS-15 looks fantastic. Ever since I saw it, I've loved the wireless aspect of it (assuming that it works well).
Two things that I'd like to say:
1. I'll suggest again to contact Hsu (if you haven't already) to see what they'd recommend. They shouldn't try to oversell you.
2. If you think that you'll second guess yourself about not getting the more expensive sub...then get it if you can. It took me a while to overcome the price tag on the SVS Ultras versus their Plus line, but I knew deep down that I would always wonder if I should have gotten an Ultra if I got something else. So, I sucked it up and bought an Ultra. With a Plus, I might have always wondered "what if?" I can honestly say that I have no regrets at all about spending the extra money on the Ultra. That comes down to the individual. I just knew that I personally would have always wondered, and because I could buy the Ultra, I did.
Best of luck in your decision. I'm sure that we'll all want to read about which one you choose!
Adam