Below are my other system specs. I am only concerned about running Photoshop CS5 while maybe I have email open. I don't do ANY 3-D work, no gaming, no video editing, no movie watching. Only concerned about how the cards would impact Photoshop. Adobe says they moved the processing to the GPU.
Windows 7 64-bit
Intel Core 7-920 processor (8MB L2 Cache, 2.66GHz)
12GB Tri Channel DDR3 SDRAM at 1333MHz - 6 DIMMs
First Hard Drive 750GB - 7200RPM, SATA 3.0Gb/s, 16MB Cache
Second Hard Drive 500GB - 7200RPM, SATA 3.0Gb/s, 16MB Cache
Power 525 W