Hmm - I've heard you mention how great the cable box seems to sound as a source, but I suspect something's just not gelling with the squeezebox / Ava DAC / etc combo that's making the cable box sound great by comparison. Could be a cabling synergy issue, and when I get back we could try some options to see if we can't dial in the sound.
Ultimately though I do think you should look at something else as a digital music source vs the squeezebox, such as a PC, windows or Mac. I've been very impressed with the sound of this Mac mini / pure music / audioquest dragonfly DAC combo I took on the road. Very musical with plenty of detail and no Low frequency issues. But Hal's server or something else could be just the ticket as well......