What kind of display and sound system do you have? If you have or ever plan on getting a mid to high-end receiver, the HD-A35 is the only player to pass all types of bitstream sound, for external decoding by the receiver. For that reason, it’s become a favorite among audiophiles.
If your TV is 1080p and can display 24 frames per second (check the owner’s manual to see if it will do “24 Hz”), it might be worth getting an HD-A30 or HD-A35. Many 24 Hz capable displays don’t do a very good job though, and often it’s best to stick with the standard 60 Hz.
If you’re not concerned with either of the above, just get another HD-A3.