Subwoofer hunt

I don't think you could go very wrong with your original choice, the JL E-110's. I have the Focal Sopra No. 2's paired with dual JL F-112's, and it's a sublime combination. (My room's about 400 sq ft.) A single E-110 would probably be enough for your size room. You could always try it out, and add another if you're not totally happy with it.

My two F-112's have had no issues for the past year. The amp fuse on one did blow, because of a failure on my receiver's muting circuit. Even though it was no fault of the sub, JL covered the repair (which was really just replacing the fuse) without any complaints. I'm sure if you actually did have an amp failure, they'd take care of you. The overall quality of these subs seem great.

I don't have any experience with the SVS or HSU (I've heard the REL's, was in a totally different setup and room though). Do they sound as good as the JL's? Maybe. I think part of what you're buying with the JL is their reputation, and quality (built like a tank is the best way to describe it). The black gloss finish is good (not as nice as on my Sopra's), about the same as what you'd see on Velodyne subs.

Good luck, I'm sure you'll love the subs, no matter which brand you go with! I do strongly recommend to go with sealed, I've had bad experiences with non-sealed designs in the past (especially for music).

@spoutjack Did you try the E-110's before, and didn't like them? Or were you just avoiding them based on concerns of amp failure? I don't have any experience with the Rythmik, so it's hard to say. I think it's hard to go wrong with the JL's, but if you have the time and patience, there's lots of alternatives out there to try! Even better, buy both, and sell or return the one you like the least.

Also, regarding connecting the sub either line level or speaker level, I'd try both. I've heard arguments both for and against, the best is to try both and see which you like better. If you're using an integrated amp, speaker level inputs are almost a must (unless you're like me, and only use the subs for home theater / digital music).