Poppyhome...were you running both the Classe CDP-202 and the Berkley DAC through the MX-120 and what inuts were you using on the MX-120? I ask because I believe you may be negating the Berkley DAC because by connecting it to the MX-120 don't you end up using the the MX-120s internal DAC? I seem to remember reading here that one of the inputs on the MX-120 bypasses the internal DAC in which case if that is what you have your Classe plugged into, then that might explain the disparity.
Not being able to get a center image definitely sounds like there is something wrong with the set-up with the Berkley DAC. I have heard the Berkley DAC and it is right up there with some of the best digital I have heard in terms of resolution, transparency, spatial cues, etc... It is not my sonic cup of tea, as it is a bit too sterile for my tastes but it is still an excellent DAC.
I suspect you have a set-up issue. I will let others who are more exert on Macintosh gear and secifically the MX-120 maybe hel you figure out what is the issue.
Speakers/Amp/Preamp: Thiel CS2.4 / ARC Ref 110 / ARC Ref 3
Sources: Basis 2001/Graham2.2/Nagra BPS/Benz Micro Glider SL, ARC CD7, Oppo BDP-83 SE
Cables/Power/Other: Nordost Heimdall ICs, SCs / Shunyata Hydra 8, Shunyata Python Helix PC / VPI 16.5, HRS Nimbus isolation system