I did testing on a K6-2 300Mhz, and yes it has 2 ISA slot, one of which is where I put the Sound Blaster 16.

Compiling an SDL port of Quake quake gives you 90% performance at 320x200 and 97% at 640x480 compared to the original. That's about 45fps which isn't bad I think.

SDL3 should now work with any i386+ with a VGA and 4MB of RAM which is roughly the requirements of Doom.