Nice flat repsonse curve too, having f3 at 35Hz and f10 at 20Hz from a cabinet smaller than 2ft3. Very small size, and good extension.

For even deeper extension, consider a cabinet twice that size. It will be a little more sensitive to parameter shifts, like we're talking about here, but as a subwoofer that may be a valid trade-off. Room modes will likely dominate in-room response anyway, hence the reason for multiple subs. As I said before, it's all about intended purpose.