In researching whether the Ultra High Fidelity upgrade is worth getting, it seems that there are a lot of people that say that they couldn't tell the difference. They didn't give any details of how they compared though and, importantly what their source material is. I couldn't find any person that said that they compared with good source material -- i.e., a USB drive serving FLAC files or high rate mp3 files. I suspect that if your source material is simply Slacker, Tunein, or bluetooth (or god forbid, the terrible satellite radio music which I find unlistenable) then the Ultra Hi-Fi can't do much with such limited source material. But better audio files served through USB is where the differences should be most apparent. Has anyone compared the Ultra Hi Fi with really good source material from the USB input? If you only ever listen to bluetooth or slacker, I suspect the Ultra HiFi wouldn't be able to offer any benefit with those sources.