Max read performance on WinXP

[Sandman]

I've been tasked with setting up a network of WinXP clients.
They're dual core desktops from Dell with 2GB RAM. They will be
reading files over the network (CIFS), processing them and writing
them back to the network drive. The files are large (400MB) and the
reads will be sequential. Network is GbE.

Assuming no server bottlenecks, how fast can I expect the WinXP
clients to run? I realize best case is 400/125 ~ 4 seconds per file.
But I have to wonder if the client can read that fast.

Has anyone here run performance benchmarks of large file reads?

Thanks,
Sandman