I'll chime in.....Don't usually post here, but I can't keep my mouth shut.
I would recommend the Dayton Titanic 15" MKIII Kit from Partsexpress priced at $688. It is getting great reviews on the AVSFORUM right now.
http://www.avsforum.com/avs-vb/showthread.php?t=602452.
If music is equally as important as HT, then a sealed design might be of more interest. This sub will not go as low as an SVS or HSU, but still extends to 20hz will relative ease. Best I can tell from the reviews, the Titanic is fantastic in the musical bass regions 30hz-80hz.
I've owned the Rocket UFW-10 as well. Although, great for music in a small to medium sized room, I would not recommend it in a large room or medium room theater duty. It's a great little sub for music and probably does a better job than the others can, but it's not in the same league as the others you are looking at for HT.
I'm ordering the Titanic kit tomorrow. As it came down to the Rocket UFW-12 and the Titanic kit. The reviews have talked me into the Titanic......