S15 or S12 with Stealth 8?

[conmoto]

I enjoy my Stealth 8s through the DC-1, but I'd like to experience more extension into the low frequencies. I'd have to run the sub via RCA as the Stealths are using the balanced connection. At least I believe both balanced and RCA are simultaneously active on the DC-1. 

Are there any characteristics of the S15 that might not play well in a 650sqft finished basement with 7' ceilings? Can the S15 be tamed and tuned for less dynamic listening? I've never owned a 15" sub. For all I know, it's an obnoxious monster meant only for home theater impact. Any reason the S12 would be better?

Also, the S12 & S15 cutoff at 65Hz. How much LF overlap is usually acceptable between mains and sub? The Stealths are -3db at 35Hz. I have much to learn regarding LF overlap. 

[garbulky]

The Stealth 8 has some serious bass extension. If you are looking for even more then you probably want at least two subs and ones that extend low. I've heard the Basx 12 sub and it was pretty good imo. So you'll probably be well served with either one. But I would probably go with two 15's! Mainly because I'm concerned about the need for low extension.
No it won't be "too much".
Also to get more impactfull bass you should try room treatment. Though room treatment has little impact on bass absorption because the bass frequencies are low it clear up the mid range and treble. The muddiness here can make you feel like the bass is "muddy" or smeared. Also carpets and curtains make significant difference.
After room treatment I feel that my bass has more impact and less smear. But I know that my room treatment is insufficient for bass treatment. But treating the other frequencies help make the perception smoother imo.

[creimes]

At the current sale price the S15 is a smoking deal, SVS also has their SB12-NSD subs on sale for $399 each, I would go two of the SB12-NSD over one S15 unless you are really wanting to stay Emotiva.

www.svsound.com/pages/subwoofers

[audiogeek]

I know the 8s go lower, but I’m running the S12 right now with the Stealth 6s and it blends perfectly in my med size room. It sounds fantastic for music, but if you’re looking for perfection in home theater, you might want 2.