Have also had great succes with a Quadro FX3800, and several Quadro Mobile Cards - But it´s really a waste of money, if it´s only for Revit (Another story if you also use Max)
I just ordered a new box last week, and expect to have it delivered today... Since i´m not using Max anymore, I´m getting a much cheaper ATI Radeon HD5770... NOT on the supported list, but it´s probably gonna be just fine... I´ll let you know when I´ve tested it for a few days.
Complete specs, for the new box:
Motherboard: Gigabyte GA-870A-UD3 AM3 motherboard (SATA3 & USB3.0)
CPU: AMD - PhenomII 1090T 6x3,20GHz (Turbo 3.60GHz)
CPU Cooler: Arctic Alpine64 GT low-noise cooler
Ram: Kingston HyperX 16GB DDR3-1600 DualChannel RAM
Harddisk 1: Intel X25-M 80GB SSD
Harddisk 2: Seagate 1TB S-ATAII 3Gb/s Fluid Silent (7200rpm)
Graphic: ATI Radeon HD5770
It´s better than x-mas - just can´t wait