I have a voodoo3 and a tnt2, and I am running an Athalon 800 with 256mb ram
@ 1280x1024x16 (voodoo)
76 fps normal,
55 with some smoke,
35-22 with rancid fifth circle of hell smoke.
1280x1024x32 (tnt2)
68 normal
42fps with some smoke
25-13 with rancid fifth circle of hell smoke.
The 32 bit DOES look better but you wont REALLY notice it unless you looking for it, after getting the framerate hit i put the voodoo back in. In my opinion anything more than a 8-10 fps hit is not worth the somewhat better color.