I've had mine since early June. I don't remember it being as bass shy at first listen as you seem to be experiencing. It did smooth out some over the break-in period but I thought it sounded pretty darn good right out of the box.
Compared to other good units I have tried in the past year: Lexicon RT20, Bryston BCD-1, Meridian G08, Modwright Sony 9100ES, Musical Fidelity A5; As espected, the 5400 is great for SACD playback, but quite surprising on redbook cds. That's what sold me.
Tim