Unless you’re hell bent on its looks I think you’re nuts for considering the SF sub at $3k. First, SF is not a premier subwoofer company (as opposed to Paradigm that makes some of the best subs extant IMHO), and the Gravis lll only goes down to 25Hz (-6dB), which probably is no better than your Paradigm. And BTW, it pisses me off SF doesn’t publish a -3dB spec, which inhibits direct comparison with others that do and only makes me think they’re not proud of the number. Second,, it’s a sealed sub that’s a different design from your x10 that’s ported, and I can’t imagine that makes it easier to integrate the two.
Gotta tell ya, to me another x10 makes a lot more sense on every level except looks. Then again, given you may be looking for some added depth I think an even better (and cheaper) option might be an SVS PB1000 Pro. Like your x10 it’s a ported design, but the 1000 would get you down to 19Hz (-3dB) and costs only $599. Plus, and this is a biggie, SVS offers a generous and true risk-free trial period that includes shipping both ways, and they have excellent customer service and would probably be a big help in integrating your subs. Either way, just adding a second sub is an excellent idea, and that alone is going to yield huge benefits to the quality of bass you’re getting. Ok, that’s all I got. Hope it helps, and best of luck.
Gotta tell ya, to me another x10 makes a lot more sense on every level except looks. Then again, given you may be looking for some added depth I think an even better (and cheaper) option might be an SVS PB1000 Pro. Like your x10 it’s a ported design, but the 1000 would get you down to 19Hz (-3dB) and costs only $599. Plus, and this is a biggie, SVS offers a generous and true risk-free trial period that includes shipping both ways, and they have excellent customer service and would probably be a big help in integrating your subs. Either way, just adding a second sub is an excellent idea, and that alone is going to yield huge benefits to the quality of bass you’re getting. Ok, that’s all I got. Hope it helps, and best of luck.