If you make your goal clear, you might get more appropriate or directed feedback. As for the feedback so far, I don't think it is off-base. People naturally jump to the conclusion that you want to do some sort of gaming (practically the only recognized use for upgraded video cards these days). Of course, this does completely ignore the rich history of video cards that were bought mainly for
2D performance back in the day of the PCI Macs...
What do you want to do with said 6400? That makes a huge difference as to what video card is "good enough." The number of PCI video cards that will work in that Mac is actually pretty staggering, but if you are looking for
better performance than the on-board video, the pool of cards is a bit more limited (well, okay, just about anything is better than Valkyrie video).
You could put anything from a Radius Thunder
30 in there to a ATI Radeon 9200. In between you've got cards like the TwinTurbo 128, Imagine Number 9, ATI Xclaim, Xclaim Pro, Xclaim VR, Xclaim 128, Rage 128, Formac Proformance III, 3DFx Voodoo, Voodoo 2, Voodoo 3, Voodoo 4, Voodoo 5 (best, IMO, for OS 9 games)... The list goes on.
So? What do you want to do with the Mac?
You may find that you get more bang-for-the-buck by upgrading the motherboard to a 6500 because then you'll get upgraded graphics (ATI Rage II+ which kicks the Valkyrie's butt in all respects) and a faster system bus at the same time without taking up a very valuable PCI slot. Of course, you do lose 8 MB of system memory when you do that, but you also gain 2 MB of dedicated VRAM allowing higher resolutions and bit-depths while not reserving precious DRAM...
Peace,
Drew
[edit: Oops! Thunder IV is NuBus! Clearly, I meant Thunder 30.

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