Re: Advice on new build
It depends what your budget is. Personally I would stick with the i5 2500k that you picked. Saves you some money, and especially if you overclock the i5 is a really good performed.
You cant just add the 'EVGA X58 board' to the current build, that only supports the i7 CPU, not the Sandybridge processor you have picked..
If you dont mind spending the addiotnal cash (I guess it will be $100+ perhaps as a guesstimate) for a little bit more performance, then ok. You will get pretty good gaming performance as it is out of that rig. So unless you are doing REALLY high end stuff, or dont mind spending the extra $$$ stick with what you have.
Just my opinion