Alright go to Amandtech Bench and do a comparison of Q9650 and i3 2100, they trade a few frames in the games listed, and except for a few aps favoring true four cores the I3 wins on all counts. This is the entry level Sandy Bridge "I" chip, about $110 on sale.
An H61 motherboard will replace your 680i for about $60.
2X4 GB Ram starts from $35 or so.
IOW for about $210 you can be gaming like you bought a Q9650 for your board. The only question is, is your operating system transferable??
Just being meself.
0pps looks like I5 2400 at $180 minimum. $270.