GIGABYTE "GA-K8NF-9" NVIDIA nForce4 4X Chipset Motherboard For AMD Socket 939 CPU $117.00
AMD Athlon 64 3000+, 512KB L2 Cache, Socket 939 64-bit Processor - Retail $146.00
Sapphire ATI RADEON X300 Video Card, 128MB DDR, 128-Bit, DVI/TV-Out, PCI Express, Model "100591L $78.00
So we are looking at $13.00 more for the PCI-Express version. I'm guessing he will get a little less performance from the Video Card, but will have the most recent hardware, which will allow for better upgrades in the future.
How does the PCI-Express X300 compare to the AGP Radeon 9550? I don't think he will be doing any heavy gaming like Half-Life 2 or Doom III. It will mainly be for running dual monitors, general surfing, and other general stuff.