If it's a core2 anything you're looking at likely replacing most of the hardware if you want to see real improvements. Core i5/7 architecture is different and a lot of mobos that have come out since then are a lot more able to make use of them than ones from the predominantly core2 era.
Lucky for you, toms just did another SBM:
http://www.tomshardware.com/reviews/...lock,2659.html
Even ignoring overclocking, this does pretty ok for stuff that's out *right now*. Overclock it and it does even better.
If you want to futureproof, look to spending more along the lines of $1k (http://www.tomshardware.com/reviews/...-gpu,2655.html)
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