Luke, there are folks who done some mods to the 4core to run 4 gb DDR2 800. I've seen several posts on it - you'll have to look for them as at least one walks thru the steps to allow the bigger DDr2's.
Thanks that's sort of reassuring. I had noticed when people put their rig specs under their names some had configurations that betrayed the spec sheets.
I don't find the information as easy to come by as I do for programming where there are blogs and extensive articles written for people of all abilities.
In my own blog, http://www.lukepuplett.com, I can spend a couple of days putting together diagrams and copy for the greater benefit of the community, I'm sure such things exist in the world of extreme hardware performance, but I just don't know where to look yet.