btw: the fastest PC cards available are PC-on-a-card systems (for ISA of course).
I've had a Siemens 486DX2/66 inside my A3000. Ran Win95B pretty well (64 MB, ATI Mach64 VRAM, 4 GB IDE HDD). But these things don't bridge anything - if you want to talk to Amy, you'd need NICs on both sides or similar. I used a serial connection which was quite a bit of pain.
And still pretty slow in comparison to the TBird 1 GHz that was standing right next to it...