If you're looking for a specific card, this is in my office Dell Optiplex workstation, I think it's an EVGA, it was ~$50 at the time.

01:00.0 VGA compatible controller: nVidia Corporation GeForce 8600 GT (rev a1)

Debian Lenny with nvidia debs from non-free, dual 19 inch DVI monitors

It's not that expensive with the price of drives these days. The nice thing about a mirror is that if your controller (or something else if you have a software raid) dies you can mount one of the drives on its own. After dealing with a failed controller, I'm glad to fork out a little more money for the piece of mind.