Could you give us a budget? Also, if you can afford an i7, go for it, a better cpu is just that, a better cpu, as long as you don't detract from other necessary components. Get 16gb of ram, 8gb is not enough for the future, there are far too many developers making simple console ports which eat up memory. As for the PSU, if you aren't going to run sli in the future, which tbh I wouldn't, you can settle for a 550watt, have a look at the seasonic g-550, its a semi-modular, and high quality psu.