IME: The GA TRP is wonderful. The Poseidon is clearly better. I can listen to the TRP for days deliriously happily. Put the Poseidon in, and it takes only a few seconds to hear the improvement in detail, extension, ambiance retrieval, spacial cues, image solidarity and holography that takes a notable step up in realism. The GA TRP is better then many $15K-20K DACs I've head-to-head tested in my system to my ears, and you have to sit and really listen carefully to hear differences between some great DACs in this price range...the Poseidon, however, is appreciably better and you instantly feel its brazen, beautiful, beguiling presence in your system in the first bar of music. Or at least so in mine.
The Poseidon is Olympian in its volume control/pre-amp function as well, being superb even directly running all 3 pairs of outputs simultaneously (i.e., 4 mono blocks and 2 subs for movies). I've had other great DACs with volume, but only the Poseidon keeps the energy/drive/clarity/detail the way a good tube or SS active preamp does even at low volumes where other DACs fall flat and sound lifeless. Quite an accomplishment!