Many ppl say PicassoIV but I truley belive the CV3D with the Scandoubler module is as good.
With a CV3D already on the way, go on the hunt for the scandoubler... the PicassoIV is just damn expencive (the scandoubler should only set you back a 50$ or so wheres the PIV often are ebayed for more than 200$).
There's also the option on of a CyberStormMK3/PPC + CyberVisionPPC + CMon but it's a costly affair (500+$).
The difference between the PIV and CV3D is so small that it's not realy a factor if you're looking for speed anyway... If that is what you're looking foor get hold of a cheap PrometheusPCI and a Voodoo3 card combo. It's WAY BETTER than any native Amiga graphic card, it's cheaper than most other options taking into conncideration that it's newer hardware and cheaper to replace parts (139$), gives you extra PCI slots to put FastEthernet cards on for cheap (10$ instead of 50$). You'll have to get an extra scandouber with that and for that I recomend the Scanmagic. This option doesn't switch automaticly though but even a monkey can handle a switchbox. ;-)