I think your review of Pod is a little inaccurate. I've read lots of threads comparing the MMX version with the Pentium version, as well as the 3dfx versions. From everything I've read, there is not much difference between the Pentium and MMX versions.
Most people agree that the main difference is in the sound alone.
The sound seems to take advantage of MMX but not much else. The real difference is between the 3dfx version and the regular version. In fact, it appears that a good 3d card will blow away MMX anyday, and that MMX seems to be overhyped. Both of course is the best, but when someone who is a gameplayer is deciding on an upgrade on a budget, a good 3d card is money better spent. I get 60fps 640x480 in Descent2.