Best card? Depends on a lot of things. Games? FPS? Visual quality? Raw power? The eye can only 'see' up to ~65fps, anything over that is ???
IMHO (in my humble opinion), the Kyro chips are the best. They don't render what won't be seen. When the new ones come out w/core & memory clock speed = to the ATI & nVidia :grinthumb
For visual quality, the edge goes to ATI. That said, there are Oxygen Labs $$$ nVidia based cards that will rock an 8500.
The Kyro guys are struggling, ATI is making moves & nVidia has the major share of the market. Support/compatibility is the major issue.
Cooling & memory ns are the differences between 'stock' & 'company' built cards. Look for heatsinks on the RAM, big fans on the chip & low (5 or 6) ns on the RAM. Gainward/Ledtek & some others build for overclocking/performance enhancements in mind.
That said, I have a VisionTek GeF2 MX 400 64mb that factory clocks 200/334. I have it up to 212/343 w/an extra fan & it works great for me.

It's a PCI (not AGP) because that's what I needed. ~$70 US.
Processor, bus speed & computer memory also matter. If it is slow going from the HD to the video card ... no point in a high end card.
Thanks for listening/reading & nice board here.