I have always found the Sony MP3 players to have excellent sound quality. IMHO, the X series has better sound quality than the E series, buy also comes with a lot of toys (touch screen, web browser) that you might not need.
If you don't need all of these toys, the S series would make an excellent choice, with a sound quality closer to the X than the E.
how long can you wait?? I think the Android based walkman is out this year..I almost upgraded my 808 to the X but decided to wait for the Android and as nothing is wrong with my old one I felt it worth it ....been very quiet on the net about it for quite a while though