traffic stats wan<->lan - ntop or better?

[Joao Clemente <jpcl@rnl.ist.utl.pt>]

I had a look at my ISP billing page today and I got somewhat suspicious 
of something wrong with the reported traffic... I had just finished 
looking to my calamaris report and the calamaris report had 1/3 of the 
traffic reported in the ISP billing page...

I decided to get some tool to analize network traffic so that I can 
understand what am I paying for... I have the feeling that ntop is the 
tool to use, but has someone a better suggestion?

My setup is

ADSL Router  ---- MyServer/Proxy
               \- hub -- Other Lan Machines

so altough my server is not the gateway, I think ntop analises 
everything that gets to the machine interface (promiscuous mode)

Any other suggestions?
Thanks
Joao Clemente