Everyone knows what they have is best.
Well I certainly don't think what I have is best... but for the price maybe.
I went with the Emo Ultra12, actually two of them since they were on sale and with the added $50 off it was a nit over $800 for both. I've done a little critical listening with just one and with both running. In a room your size I wouldn't have bothered with a second one possibly - but having heard multiples... now I can't see listening to anything (even 2ch music) without at least 2 subs.
I don't care about the wider dispersal as much (it's just my wife and I so there's really no problem with both of us sitting in the sweet spot) - but it's the dynamics that really make the difference. If I had twice the budget I allowed myself... then I probably could have gotten by with a single 15" with 1kW or more on tap and not ever known different. I have a somewhat larger room that opens to two larger spaces - but I run my subs barely over the first line on the gain dial... and they can easily hit peaks ~100db at that - which is all I require as I don't like to play for the whole neighborhood, and it's very smooth and 'invisible' - i.e. sounds like I have monstrous towers in the room rather than small standmounts.
I'm sure that SVS will sound sweet as well - maybe even a little more dynamic. In any case, I wouldn't bother with a 10" - after all, you might move in the future and with a good sub (or 2)... it should still be running strong.
I don't think you can really go wrong with any of the 12" offerings from SVS, Emotiva, HSU, etc... but I agree with sealed being the way to go. I've only had ported subs until I bought the Ultra12's and now I can't hear them as being anything other than 'sloppy' (ported subs I mean). Granted I didn't own anything very high-end that was ported, so I can't really make a blanket statement to that effect.
The really nice thing about subs is that you can pretty much just shop by specs, FR charts, and word of mouth... there's not nearly as much subjective analysis required as there is for loudspeakers. Either the bass is there at a specific frequency or it's not... timbre doesn't come into play at these levels so it's more a matter of how low and how lound you want it to be. And how much you're willing to spend to get there.
