I might instead demo a new source and preamp. You might recover (find) all the bass you need sight there. Depending on your tastes a sub may be unneccessary at that point. Or maybe try the Mye stands. That should work for most acoustic (except 'blood and thunder' classical) and electric (some jazz and most rock) music unless you need extension below 37-40 cycles or you need to "cave your chest in." You might be suprised that you don't need a sub. But it's up to you.
If you must get a sub, check out REL, Velodyne, or DIY designs based on Dayton or Adire driver. The best are likely to be the Linkwitz dipole sub (DIY design) or a set of Magnepan Tympani 1D panels acting as a sub with a 500W+ buiser SS amp. Though the tympanis play to only 30 cycles or so I believe. But that should be the most "seamless" sub, or it should be.
If you must get a sub, check out REL, Velodyne, or DIY designs based on Dayton or Adire driver. The best are likely to be the Linkwitz dipole sub (DIY design) or a set of Magnepan Tympani 1D panels acting as a sub with a 500W+ buiser SS amp. Though the tympanis play to only 30 cycles or so I believe. But that should be the most "seamless" sub, or it should be.