Duncan & Acid,
I think it boils down to.....which sound characteristics do you prefered. To me, both are excellent discmans. They are way better than the newer generation discmans (i.e. ej01, ej925, and ej915).<----Headphone out.
If you prefer *fun*, D-777 will definitely be the one to go with. D-777 delivers very powerful sound (very tight bass, good midrange, and slightly less high). The soundstage appears closed and much narrower than the 900. Sometimes the midbass can be a bit over done here.
If you prefer *accurate* with sense of air, D-900 is definitely your discman (a bit medicore in bass, excellent midrange, excellent high) The soundstage is also much wider. Lately, I actually prefer the D-900 over my D-777.
Others 2 discmans worth mentioning are D-303, and D-515. D-303 share many aspects of d-777's. However, everything that the D-777 is capable of...the D-303 can do it better (very deep bass extension with a bit of midbass boost, warm sounding, very sweet midrange, and good high). The soundstage is also wider, but not as wide as the D-900.
The 515 is also an excellent discman. It sounds very similar to the D-303 (lots of sub-bass, no midbass at all, sweet midrange, and good high). It I ever ranked my Discman according to my preference it would go like this:
Headphone out:
D-303 > D-515 = D-905 > D-777
Line out:
D-515 > D-303 >> D-E905 >> D-777
I just like the D-515 than the D-303, b/c it allows user to adjust bassboost/DSS while the line out is being operative. Otherwise, thier line out is equally impressive. D-515 and D-303 line out is significant better than the D-E905. Meaning, better bass extension, much wider soundstage, and very nice clarity. The midrange b/w the top 3 players are equally impressive. The 905 is a bit congess when compares to the 515, and 303.
However, these results is based on my judgement only. Some people might find these results to be different. I used Senn HD-580 + creek obh-11 to test the line out. I used Sony MDR-E484 and Grado SR-225 to test the headphone out. I hope this help.
I didn't include the D-555 in this list, since my friend still have it. I'll have it back shortly though.
D-777 sounds much better on my E-484 compares to the bigger headphone.
Purk