What games are you playing and which socket does your motherboard have?
I don't know if you're asking about Lynnfield or Sandy Bridge so I can't really help.
I read 2007-2008, so I'm guessing you've got 1156. In that case, wait till later this year and get something based on the Ivy Bridge because the SB requires a new motherboard anyway and it's a big performance leap over the old stuff for about the same price. If you're in a rush, the Core i5 760 is cheap and effective but given no other details (PSU is very important) I don't even know if your laptop can handle it.
EDIT: Woops, thought you were upgrading your laptop not replacing it. In that case I'll repeat this: wait till later this year and get something based on the Ivy Bridge.