[Samba] Samba Transfer Efficiency

[Henri Cook]

Afternoon all,
I'm running a transfer setup as follows:
A -> B -> C - fairly simple, B initiates a transfer from A to C - B is a 
vital intermediary as it bridges two otherwise seperate networks.
All machines have onboard Gigabit ethernet, A+B are connected via 
Crossover and B->C is connected by very fast switch (i.e. all 
connections should be able to use the full gig if they wanted to)
I see an average of about 23-25% usage in both the crossover (A->B) and 
the connection (B->C) - are there any tricks you can recommend for me to 
speed up my transfers?
Box A is the box running Samba 3.5.1-42.el5
Box B is Win Server 2003
Box C is a NAS (BSD)
I've found a lot of what seems to be outdated information online like 
changing my SNDBUF to 8192 so I thought i'd drop an email to the list 
for more up to date information.
Many thanks,
Henri