Agree with Ashish. Pentium to i3 is only a half upgrade.
If you are OK going used, you can find less popular i5's for under $150 on ebay. And since they couldn't be overclocked, you shouldn't get any fried ones. For example, I see i5-2310 going to for $120 all the time (that's what I have) . I play bf3 on 1080p ultra at over 60fps in 64 player online with that processor.
Edit: of course since I said that there are non on ebay today, but completed listing show that go for pretty cheap in auctions.
i3's already considerably lag in BF3 on 60 player maps, think BF4 is gonna be any better ? Or any software titles in 2 years.. no
Is it because it was on ultra? I don't play on ultra because fps means more to me. With my rig right now, I'm okay with the fps. But my problem is frame drops and sometimes it freezes.