Ok, so here's an update based on what I've been told here and elsewhere so far and a somewhat in-depth comparison of the different choices.
Budget update: I don't have a set budget per se, but I don't think I want to spend more than $2,000, and that's really stretching what I want to pay. A big factor for me is the size: I don't want a massive box taking up a lot of space, and the larger it is, the less likely I will be able to position it perfectly. I'm open to two, which it basically sounds like I will need to do, but I flat out don't have the room for more than that.
Here are the options I'm looking at (all of which are highly recommended and very capable and high quality subs based on my research and what everyone has told me so far) and some comparison details on them (dimensions are DxWxH, price is for each/pair):
PSA XV15: 21-200Hz ±3, 22.00 x 17.0 x 23, 75lb, $800/1518, 30 day trial (buyer pays S&H (both ways?)), 5/5 warranty (with free S&H?). Could possibly mix with XS15 ($750) for a tighter more accurate sound although I'm guessing this would be negated by the XV.
Rythmik F15: 14-200Hz ±3, 21.50 x 19.0 x 19, 102lb, $974/1948, 30 day trial (unclear who pays S&H), 5/2 warranty (buyer pays S&H). Could possibly mix with the LV12R ($590). I realize the FV15HP would be better than the F15, but it's a lot more expensive and more than I'm comfortable spending.
Hsu VTF-15H: 16-200Hz ±?, 27.75 x 18.0 x 26, 100lb, $880/1760, 30 day trial (buyer pays S&H (both ways?)), 7/2 warranty (NO WARRANTY INFO ON WEBSITE). Could possibly mix with the VTF-3 MK4 ($650) or VTF-2 MK4 ($530).
Outlaw LFM-1 EX: 16-180Hz ±2, 24.00 x 17.0 x 21.5, 80lb, $694/1388, ?trial?, 3/3 warranty (buyer pays S&H)
SVS PB12-NSD: 18-150Hz ±3, 22.00 x 17.3 x 21, 66lb, $770/1540, 45 day trial (free S&H), 5/5 (free S&H). Could possibly mix with the SB12-NSD.
Here's my impressions:
PSA: Warranty second only to SVS (which makes sense considering the common history). The cheapest option except for the Outlaw, which is only a 12-inch. Down-firing, though from what I've read there's really no difference to front-firing. The relatively high bottom-end concerns me, and it seems particularly odd for a 15-inch, but from what I can tell I should expect it to get much lower inside, and if I'm understanding correctly they are putting out the CEA numbers which don't look as good whereas everyone else puts the real-life performance ones which look better. The other concern I have about this sub, even though I see it as a big advantage as well, is that it weighs significantly less than the others.
Rythmik: Most expensive option (and that's with the sealed version, vented version is far more expensive than the other options) and a so-so warranty. I really like the idea of the servo, which based on reviews I've read seems to make anywhere from a slight to a substantial difference, and I want my bass to sound clean.
Hsu: Massive, so-so warranty (with no info on the site about it other than the duration), and second most expensive option. Not to say I wouldn't end up going with this one, but I'd really have to be talked into it.
Outlaw: Cheapest option, but only a 12-inch, in a box the size of the PSA and Rythmik 15-inchers, and worst warranty. Doesn't feel at all like I'd be getting much bang for my buck, in fact looks like the second worst value. Like the Hsu, I'd have to be talked into this one.
SVS: Best warranty and return policy by far, which makes me want to go with them if for no other reason than if I'm unhappy I just send them back and get all my money back. Only 12" though, for the same price and size as the PSA 15's. Bill of Rights aside, this looks like the worst value. And to step up to the next model up in the line is a big increase in price.
I'm really leaning toward the PSAs right now, but would like input from everyone. Secondarily I'm leaning toward the Rythmiks because of the servo and resulting clean, clear bass. Of course, I'd like have at least two if not three strong options so I can price shop, see if I can get a deal on b-stock or with military discount from one of them.
Some final questions:
- If 2 subs produce the output four times that of a single sub, and a single 12" is enough for 2-3000ft^3, it seems that 2 12's should be plenty, and 2 15's should be more than enough. Why is this not the case?
- My little (10"?) Polk sub is enough to add some decent bass and for me to even feel it just a little bit on the couch, and it's at 3:00, yet I'm being told (and I believe it, not trying to say they're wrong) that for my space I'll need at least 2-3 15's or maybe even some 18's. This just doesn't make sense. Can someone please clarify why I would need so many times the driver area and amp power for what seems like it should only need to be a 4-6x output? Again, IRT the last question, that should be able to be gained just by adding another sub of the same size based on what I've read. I'm obviously missing something.
Thanks to anybody who managed to make it all the way through, and for any input you can give.