I own most of Aphex's shit, but have gone off most of it in the past few years. His recent release 'Syro' is amazing though, a generally just listenable and a bit more, uh, mature? sound. The computer controlled whatever ep2 just afterwards is pretty great too.
Autechre - Exai is actually my fav release of theirs now, cranked it quite a lot, and the LP package is really nice
Otherwise everyone else has mentioned most of the usual recommendations... Boards of Canada comes to mind, although I only really like Tomorrow's Harvest tbh.
I used to listen to so much of this shit back in the late 90s/early 2000s