I'm currently putting together my upgrade plan... what I'm thinking of doing is
1) Buy a 3570K
2) Buy a bottom-end sandy bridge board plus 4GB RAM
3) Put the 3570K in my ASUS P67 Deluxe (and rest of my current machine)
4) Put my 2500K in the bottom-end SB board with the 4GB RAM, and combine that with the spare PSU/case/etc. I have.
That way I'll have two fairly decent machines, one for gaming and Windows stuff, and the other mostly for BackTrack and the many other uses I have for a spare system.