In order for me to answer your question please allow me to mention that my preference is on music listening first and foremost. As such, I crave the tight, punchy, and very well articulated sound w/vast distinctness in the transients. I will have it no other way. You can go so far as to say that I am admittedly very picky. Can't stand one-note, sloppy, boomy, and overhung bass. Honestly, it drives me crazy. By now you get the idea, no?
Right now w/the Hsu ULS 15 MK2 sub for $806 shipped is a steal to say the least! I am NOT aware of any other sub for the money out there right now that can best it. If there is, then I want to know about it. BTW, I also do like to watch a movie every now and then. The ULS 15 MK2 is no slouch in that department as well. It packs quite a wallop if you will giving you a visceral experience.
As far as getting one now and then saving to get another goes, my advice is to go for it! You will NOT regret it. Hsu offers B-stocks from time to time so check that often. Mine was a B-stock and it worked perfectly. Honestly, I never could find anything wrong w/it. But, I sure loved the discount that I got. Anyways, best wishes to you and on your decision!
Cheers,
Phil