128K MP3's are acceptable IMO, but not nearly as good as CD. 256 and up is getting pretty close to indistinguishable from cd. I use FLAC for my streaming to the 3808 and try to keep all downloaded stuff as high as possible sometimes 128 is all I can get.

Jason
M80 v2
VP160 v3
QS8 v2
PB13 Ultra
Denon 3808
Samsung 85" Q70