samba - Jul 2007 - tune Samba NAS video server and Windows XP clients ?

Hello,

I need to tune Samba for maximum throughput.

Our NAS server is  used for MPEG2 viteos storage. We stream  and copy
files at the same time.

Network is a full gigabit  : switch Linksys SRW2016 (jumbo frames
enabled) + category 5e wire

Does anyone has got an idea  of  which is the theorical throughtput  of
Samba ?
Currently I have +o- 20Mbytes/Secs ...
On big files I can go up to 40Mbytes/Secs

With AppleShare+Netatalk  I can got up to 60Mbytes/Secs

How can optimize Samba or my system or clients to boostup transfers ...

I've get my config from FreeNas. My samba is setup to act as Wins Server

[global]

   workgroup = MSHOME
   server string = %h server (Samba, Ubuntu)

   wins support = yes
   dns proxy = yes
   name resolve order = wins lmhosts host bcast

   socket options = TCP_NODELAY IPTOS_LOWDELAY SO_RCVBUF=16384
SO_SNDBUF=16384
   use sendfile = yes
   os level = 65
   read raw = yes
   write raw = yes
   max xmit  = 65535
   oplocks = yes
   deadtime = 15
   getwd cache = yes
   strict locking = no

   large readwrite = yes

Any tips or ideas are welcome
Regards