Let´s face it.
If you have a good AGP MoBo and processor, you need only to upgrade in the video cards.
If you have already in your system Gainward 7800GS+ 24PP AGP, you don't need to upgrade any video cards (at least til NV8600).
Windows Vista, Blue-Ray drive, DX10, PCI EX 16X, DDR2 and etc. you won't need them until 2010. Let them mature first.
PapIacoz
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ABIT IC7-max 3
P4 EE 3.2GHz/ThermalTake Big Typhoon
Corsair 2GB twinx DDR 550
Gainward 7800GS+ Golden Sample AGP (24PP)
WD Raptor 2x150G RAID 0
Creative X-Fi Fat@l1ty
Lian-Li 6070B Black
SeaSonic 700W