Well I3 has a locked multiplier so no OC. I5 and I7 K series can OC.
The PSU its HP one so you dont need a bad PSU.
I suggest to get I3 now and later in future get I5 . Or get I5 now if u have the money.
And never go cheap on PSU. Its the most important part of it.
So recheck the build i posted that is great.
Also you can use the HDD from your current pc and save money.
Choose a case and buy what i linked. http://pcpartpicker.com/p/q7xc