i recently upgraded last month (my bday) from 2GB 2x1GB to 2x1 + 2x2 GB of xms2 800mhz
naturally i didn't notice much of an improvement in xp32.. however using vista 64bit ultimate has been a pleasure from the upgrade onward
i am a multi tasker however.. i.e...
mirc 1 server anywhere from 5-15 channels + usually 2-8 Pm's..
msn anywhere from 0-10 msn windows
firefox anywhere from 1-15 tabs between 1-2 processes.
pspad (another code edit program, used for comparing files)
and sometimes a game alt-tabbed out such as AOC.
the system seems much more responsive in such conditions.. able to tab-alt outa the game quickly. and nearly as fast back in. even when the ram isn't "full" it seems the bandwidth increase helps even!
and with ram to spare. i have thought of having a vmware IRC bot for my clan channel setup..
you can't really go wrong.. i paid like 86$ to get matching sticks.. for 4GB! that is a great deal! (let alone even cheaper possible)
i say go for the 6GB total + 64bit os
edit: quad channel still works on my board!
(must update that board info *runs to do so*Edited by uberjon - 9/7/08 at 7:25pm