P35 chipset, PCI-E 1.0a/1.1 - bottleneck?

[VirtualLarry]

CPU is a Q9300 @ 3.0 / 400FSB. PCI-E freq 100Mhz.

Any idea at what level a card will bottleneck on this system?

For an added twist, say I do more distributed computing than gaming. Is it still a bottleneck?

 

[DominionSeraph]

Pretty sure DC tends to be light on file transfers. You shouldn't be moving gigs of data back and forth, so it should be a non-issue.
And from what I remember, 1.0 doesn't become much of a bottleneck until ~GTX 580 speeds anyway.