I'm going to assume that you have VLB. The Diamond Viper P9100 was a pretty hot card. I think I still have the PCI version kicking around.
These cards were pretty awful performance wise in DOS. Remember, they are really two video cards in one, basically a VGA card with a dedicated graphics accelerator chip (The P9000 or P9100). They used a crappy Oak or Weitek 5186 chip for bog standard VGA support and VESA BIOS Extension support required a DOS TSR in order to work right. The Weitek P9000/P9100 with proper Windows drivers was very advanced for its time however.
I'd assumed that it was going to be under Windows, but maybe that's not warranted. I've got a Tsenglabs something-or-the-other in my 486 box in VLB. Seems to be okay. Wish I could remember the chipset, though. 4MB RAM.
Really, any card is going to suck in 16-bit DOS mode. Things start to fly when you can use a 32-bit instruction set.
Personally I have the S3 Trio 64 in VLB that should be pretty close to the best VLB. I wanted the S3 968 version that comes with VRAM, but the last auction for one of these went beyond what I was willing to pay