The difference between the D777 and the E905? so far as I know apart from a couple of minor chip updates, the biggest change is in the DAC ~ Both are made by Toshiba (also can be noted on the link posted above) but the D777 employs standard 'MegaBass' where the bass boost is added within the amplifier, and the E905s 'Digital MegaBass' is added 'On-DAC'... the E905 line out is cleaner than that of the D777, and so is the headphone out, being much airier (having quite a credible soundstage) but you can ultimately hear the begining of the end for Sony sound quality in this player...
The D777 'auto-equalises' its sound from the headphone out... if there is a huge bass drum or something playing away on your CD, the D777 will distort (between 6-8 on the volume when it begins to run out of steam) a couple of times, and then the distortion will stop, the player having EQ'd the bass to a level it can manage, and it would 'remember' that bass depth througout the rest of the CD, so ~ unless there was heavier bass on another track (where the process would be repeated) there would be no more distortion from the headphone output (but I never actually heard a degradation in the bass depth, its very clever). Whereas this is NOT the case on the E905... so whilst the sound is cleaner, and airier it does NOT have the 'auto-eq' feature, the unit can (although I've only managed it a couple of times) distort
If you like your music loud and bassy and don't mind a minor degradation in sound quality... look for the D777 over the E905... but of course it needs to be said that both players sound rubbish with the bass boost on, the D777 with its 'Auto-EQ' becomes quite spitty with the treble, and the E905 can (as just mentioned) distort (that was how I got the unit to distort if that is of any interest)