Throwing this out there just for some opinions: In a very "hard" room full of compromises, 2500cft, at moderate volumes, cutting off at 60Hz, does sub quality even matter as much, between "acceptable" and "awesome"? Most of what I'm reading is about high SPLs justifying the price differences, beyond whether it's tight/accurate.
Technical/factual question: Pipe organs not withstanding, is there any practical diff for music between -3dB points of 27 and 24 Hz? One wonders where the -0dB points are, and where real usable sound really ends at the lower end, both on my Klipsch RW-8 and the SVS...
Scratch one of my questions, since I belatedly realized that the rca-in/rca-out route for cutting off the speakers at 80Hz wouldn't work in my case, because. My DAC doesn't have variable volume output, so the two volume controls (sub and amp) would be totally disconnected.
I'm likely to try the SVS to see if it's a noticeable improvement over the Klipsch, and if I can belnd it as well. However, as a time-sensitive thing, I can currently get an insanely small 8" discontinued Pinnacle for cheap and has speaker-level outputs (the only unit I found that still had them): it would be an upgrade, but not as much as the SVS, plainly, and it runs hot. But it would allow me to do an 80Hz crossover, limiting the X-12s. I guess one thing I'm trying to get rid of is a slight reflection in the 60Hz range from the X-12 reflex ports off the walls, which I can't do anything more about (compromises whatever I do). The Pinnacle can't do much SPL, but probably is enough for my listening level, it's smaller, and rated 27Hz -3dB. So I think it would work, too, and be $200 less than the SVS. But so far, I'm not hearing much cry for cutting off my mains at 80Hz as a must-do. Doing so was what made me start browsing subs, and then I found lots of love around the forums for the way I actually have mine connected, particularly with regards to making the sub sonically disappear by lowering the xover.
...sorry for the ramble. I fully realize the correct answer is "just get the SVS and listen for yourself." But your experiences are appreciated.