Your PSU should remain somewhere above 500-600w, in this case. OCing doesn't require too much power, but I would suggest a 600w power supply.
Check out this one:
EVGA SuperNOVA
http://www.newegg.com/Product/Product.aspx?Item=N82E16817438048&nm_mc=AFC-C8Junction&cm_mmc=AFC-C8Junction-PCPartPicker,%20LLC-_-na-_-na-_-na&cm_sp=&AID=10446076&PID=3938566&SID=
And the case, it really comes down to how you feel it looks. A Define r5 is top of the line, but an NZXT S340 looks good too. It really depends how you look at it.
S340 vs Define S
H440 vs Define R5
That build should be good for your needs, but if you care, the RAM colour seems a but out of place compared to the black and white of the rest of the build.