"However, I find it difficult to get a sense of the sound quality of the unit because the reviews focus so heavily on feature sets, connectivity, upgradability, etc. They often say that it sounds nice or competes with DACs in its price range, etc."
There's only one way to get a sense of SQ. And that's to listen the component yourself. Reviews and opinions are not good enough.
" I'm at the mercy of the Music Direct/Crutchfield/Audio Advisor return policies when auditioning since there aren't any high end stores around here."
You need to find a better place to do business. If you call The Cable Company and tell them what you are looking for, they'll send you a few demo units that you can try before making a commitment. Its a much better solution than buy and return.