if its a new build...then go for i3-530...
but if you have an existing lga775 mobo. then go for the E7400 or E7500...
unless a miracle will happen today and all the apps become massively multi-threaded, there is not much difference between the dual core i3-530 & today's comparable Core2Duo...
kung gusto gyud kag i-platform nga maayo...get the i7-860...paired w/ a P55 mobo...