joden I ran a set up similar to yours at one point for testing a system.
it was a Toshiba Intel I3 with 4 gigs of ram.
it ran pretty good actually.
more than adequate for running sonar essentials and producer.
more ram will give you more headroom over plug ins,exc.
but you might find 4 gigs will be close to enough.
have you pushed it yet with this set up ?
I did and on that particular set up (the Intel I3/4 gigs) I was able to run 20 tracks with 4 soft synths and prochannel on 10 tracks/over 15 vst's.
using up approx. 31 of sonars performance module (RAM) and 40% system memory. (that includes all system functions)