I'm not particularly concerned with OS9 compatibility, I have the 7300/7600 FrankenMac for that
I'm not beyond re-flashing a PC card but the question still remains: will the gains to be had from upgrading be greater than the losses taken from going from a 66Mhz card to a 33Mhz one?
This is why I'm not terribly concerned about upgrading the video. I'm trying to keep my mind entirely on what is feasible. If I could go all-out, I'd upgrade the video, CPU, optical drive, hard drive, the whole nine yards. However, a bigger hard drive, more RAM and switching in a DVD-ROM are all relatively low-cost, high availability upgrades.