I'm not sure why you purchased these speakers if you did not like the basic sound. Did they sound better when you first heard them? Go back and find out why - room, amplification or just a good source like audiophile grade vinyl or super CD mastered by the best, could of fooled you at first glance/listen.
I don't like the SL-3 much or at least some years because they went to a ported box in lieu of the sealed box. Sealed box always sounds faster and tighter to me - unless we are talking about B&W's top of the line stuff.
Is the Aerius-i ported? I know the original Aerius is not, it's sealed - I like it like that.
Aerius: 8" - used in sealed cabinet format.................Aerius i: 8" high excursion, high rigidity cone with extended throw driver assembly, non-resonance chamber format
Eight years ago I changed my stator panels and had to replace a blown woofer - I was not angy about it, I love these speakers to death. Jim Powers at Martin Logan set me up and talked me through it all. I was getting terrible dealer service at the time so I did it all myself - he's my hero now.
I suggest you contact Jim Powers at M/L and describe the problem you are having. Your other choice is to just sell the speakers and get something that floats your boat (something you like).
PS: Good luck, remember most problems can be solved if you throw enough time and money at them.
..................maybe you should try cleaning the stats before doing anything drastic - may affect the bass in a way you don't expect.