I'd get an I3 mate, from the research i've done you can get an i3 and honsetly it will still blitz through anything (ive played boad company beta on my mates i3 with 5850, eating it alive @ 1900x1200) you can later upgrade to an i5 or i7 860 with the same MOBO ram etc etc if you start to struggle (i doubt that)
also i would go with a 5770 card at that resolution but a 5850 would be a great addition also
also i would go with a 5770 card at that resolution but a 5850 would be a great addition also