I used to own an XP-50 and now I've got an XV-5080, and I also have a triton. And I would pick the XV-5080 over the Triton anyday. Yes the Triton sounds better in the patch/prog mode than the XP-80 but that is because alot of the sounds use around 5 FX. The Roland on the other hand use mainly chorus and reverb. So when you go to perform/seq mode the Roland can be made to sound better than the Triton. As for the piano sound the xp-80's sounds alot better than the Tritons. Now as for the string sound they are both real close. But the Roland gives you 100s of ways more to edit the sounds over the Triton. All in all they are both good but you can obtain better sounds with the XP-80. As for the XV 5080 it totally blows the Triton out of the water.
And yes the Expansion boards do sound great and that is a way that you customize your synth to your likeing.
Just my opinion, hope it helps.
If you'd like you can check out my music at:
www.Mp3.com/RuslanY Most of the songs were made on an xp-50 and the newer ones were made with the Triton and a Yamaha EX5R.
PYCLAH
www.mp3.com/RuslanY