If you want a game that can push your system limits
http://www.gog.com/game/star_ruler_2 will do that... this is one of the new true 64bit games and lets you make massive (
ie. pick a silly number and double it) maps.
As for the ram I'd put the new Corsairs in slot 1 and 3 (
the dark ones) and the older in 2 and 4 but again, it really shouldn't become an issue.