Martin Logan BalanceForce 210 vs JL audio E112

Yes, JL audio is much better. Since you're in an apartment, your neighbors will want to choke you. You'll need to spend a lot on isolation platforms to avoid eviction. If you put 2 sets of 4 Nobsound springs, it might support the sub sufficiently. Isolation will clear up the upper bass and midrange for sure thus more detail.

Do you have the JL or listen to it? 

If the JL can be calibrated to your room, it might be an option.  The Perfect Bass Kit (PBK) for the ML is essential.  Having the sub's output customized to your room is not optional, once you have heard it.

I have some JL e110's and have heard both. The e112 has an even higher output and I'm using with some vintage JBL which are loud. The e110 has about the same output as my older Sunfire 12" which I also love. ML didn't have the ultra deep base to 16 Hz. like the other two. What is your ML mated with?

My setup its a 5.1 with the ML motions 30's and the 15's. Also I have not done the PBK yet. Going to see order it and see how much its going to improve the response. 

Looking at the specs of the e110 and the e112 its 25 Hz and 22 Hz can they really go much lower? 

Well, maybe. My Sunfire 12" is rated down to 16Hz. at 116dB in a room. To me, the e110's go lower than the Sunfire. Since you have ML's, maybe you want to stay with ML subs to match. The PBK sounds like the first logical step.

@noel89 Oh, if you have ML speakers you should definitely be considering a ML sub.  Beyond the PBK, ML provides custom cross-overs that match their various speakers.  I use the custom crossover that lets me run my CLXs full range, so that I add nothing to the CLX signal path, and the the sub just starts adding in bass as the output of the CLSs decreases as they go down in frequency.  I just looked quickly to see if they provide crossover files for the Motion 30s or 15s, but can't find any crossover files.  You might want to call them and inquire.