if you already have a quad core system than there is no reason to upgrade to an i7, since an i7 is a quad core with faster memory bus speed and multi threading. if you have a core duo and want to upgrade to a quad core than get the i7.

the i7 supports different memory numbers than the quad core. so my advice is if you get an i7 is: get 6gb of ram, since that is more than enough and adding 3 more gig to have 9 gig of memory is pretty expensive and the improvement from 6 to 9 won't be that much. instead use the money from the extra 3 gig of ram to buy a raid0 or SSD. since the i7 motherboard supports raid0/1 already you don't need the controller card, so it is pretty cheap. less than $200 for the 2 raid HHD.