I'm telling you, there is NO lack of bass on my brothers 9's He's powering them with a pair of Pass Labs monoblock tube amps, and runs them in extended mode.
He does NOT use a subwoofer. It's been about six months since I last heard them, we were watching films on them and they are amazing.
I personally have five pairs of near TOTL Infinity speakers right now, and his 9's output as much bass as any of mine.
Crescendo 3009 dual 10" woofers ported (two pair)
RS2B dual 10" woofers sealed
Ren 90 single watkins dual voice coil 10"
Plus I owned Kappa 8.1 til I traded 7.62 for them, and he has a pair of 2.5 with watkins 12" that are amazing
As to comments about the emits..... well, you can say whatever you want, my RS 2b emits have no airspace behind them whatsoever, simply mounted in the wood (no cabinet on top) my EMIMS are dipolar (on rs2b) mounted in the same wood.
I'd suggest going 7.62's route and replace the wood screws, but your problems lie elsewhere then the mating of the woofers to the cabinet. (amplification would be my first thought, wired out of phase would be next) you are using the original wiring harness right? 7.62 said his Kappa 8 or 9 (forget which) never sounded right with a replacement new harness.
Your 9's, do they pass the push test?
(push in one woofer, the other woofer moves out at the same rate, and after you stop pushing, they slowly both come back to rest with amplifier OFF)