Thanks David.
SSHSSH, can I repeat that you should drill down into the statistics and gain an understanding from that. I've struggled with this myself in the past but they stats are very good these days. If you wanted to test and record stats for your 2Gb test;
1) Clear all the network interface stats (we're use these but remember these will include TCP/IP protocol overheads)
2) Run your test with 2Gb of requests
3) Check the interface stats as necessary. In and Out for the 'outside' interface, In and Out for the web server interface and in and out (if possible) for the web to SQL servers. Remember that 'out' for the server interface will equal out for the client side interface.
Understand? I'm tempted to do a diagram but have no time! =]