Outside of MAME, meaning using emulators that utilize 3D (PSX, N64 & Zinc), I've found that the card does struggle when using 32bit color of 16bit.
Thats said, 16bit colors is fine for all those emulated games, and the performance at 16bit is brilliant.
I love this card, totally recommend it.
I run a P4 2.4G pentium, 1G ram, with a barebones Win98, as I've personally found it outperforms XP.