How big a downgrade is this?

[epoxy5]

Well I want to move over to the pci express platform, but I cant afford the best gfx card this time, so I am just curious about how big a downgrade I will see in games comparing these two systems:

Old one:

P4 3.2ghz htt northwood
1gb ram
6800gt 128mb agp gfx

New one:
AMD X2 4400 (1mb cache)
2gb ram
6600gt 256mb pci-e gfx

 

[epoxy5]

I will get a better gfx in a couple of months, so I just needed something in between.
Somehow I thought moving from 1gb ram + p4 to 2gb ram and the Amd chip would make the gab between the 6600 (256mb) and the 6800(128mb) a little smaller, but perhaps there is such a big difference?