Hey guys...check this tweak out..I did it and got a boost from 1125.7kbps to 1569.2 kbps!
Not too shabby eh? lol
Here it is...you will need to enter these DWORD values and names to get it to happen

HKEY_LOCAL_MACHINESYSTEMCurrentControlSetServicesTcpipParameters
"SackOpts"=dword:00000001
"TcpWindowSize"=dword:0005ae4c
"Tcp1323Opts"=dword:00000003
"DefaultTTL"=dword:00000040
"EnablePMTUBHDetect"=dword:00000000
"EnablePMTUDiscovery"=dword:00000001
"GlobalMaxTcpWindowSize"=dword:0005ae4c

To benchmark the modem speed gain I used this online Speed Test:"
http://computingcentral.msn.com/internet/speedtest.asp

Enjoy
Opus :D