I had an AGP card, I think a 7550, that seemed to handle Unreal Tournament, No One Lives Forever, etc, pretty well with a 400MHz K6-2+ and 128 MB RAM.
Doom, Duke Nukem, (and Blood, Redneck Rampage, and similar games) didn't require 3D acceleration at all - they played fine on S3 (Virge?) chip, PCI card, with if I recall 1 (maybe 2?) MB of video RAM. Even built-in video chips should be able to play those games.