I going to post some thoughts that should be taken with a grain of salt. I'm by no means knowledgeable on the technical aspects of phones.
I think Android phone SQ boils down to processing priority for third-party music players like Poweramp and others. It seems to me that when the music is sounding sharp/crisp, invariably, I can go to the task manager and the music player app is using between 18 and 30 percent of the processor (and that's regardless of single core/dual core).
The newer ICS hacked roms I've used on my T-Mo Galaxy S2 (lately) let you limit background processes. However, it also seem to allocate less processor power for apps probably to extend battery life. Meaning, even though you can lockout unwanted apps --your app of choice can only use a little of the processor. So far, Poweramp has never gone over 7 percent processor use.
The power allocation scheme of the newer Android ICS roms appears to be similar to Apple. I swear I can't tell the difference between a low bit rate mp3 and ALAC on my iPod Touch 3G. I think when there is little processing power for music there is less clarity. Plus, when you have a complex operating system, music clarity will change from time to time. Additional programs make the problem worse.
The Sansa Clip+ sounds the same every time you crank it up, and, it pairs well (from its headphone out) to portable amps, small headphones, and IEMs. It's not super clear either, but for the cost, it is the best bang for the buck.