I had this cards:
The picasso4 has a programable 24bit flicker fixer (you can see aga at 120hz), lots of expansions (like concierto paloma or pablo), and a fast gfx chip.
The CV64 has a slightly faster bus but no expansion, worse resolutions and refresh and no FF.
The CV3d as the slowest of the three bus, a gfx chip slower than the p4 but faster than cv64, no monitorswitcher or scandoubler (but you can add the scandoubler-monitorswitcher module wich will give you 18bit colour)
GVP Spectrum: too slow gfx chip and small bandwitch and poor screen refresh, monitorswitcher (but still quite better than aga)
I would go for a PCI solution, but if you insist, buy a Picasso4, it's far better.