That is not a bad temp at all! I run my 2500k @ 4.5ghz with 1.38v. (generally sits at 1.35v, but it shoots up a little bit once in a while) It is pretty close voltage and the clocks are the same and I use a H60 water cooler which is very close to your cooler in performance. I get 80C maximum in Prime95 (generally is at 75C in Prime95) so I think you are fine.
i have a cheap coolermaster 371 with four fans two in and out.
ive reaplied the thermal paste and the temps are the same and the temps are the same as well with the side cover off the case.
Well at least your case has decent cooling options.
I'd put a good 120mm in front like an R4 Sickleflow.
And use 120mm x 2 in top exhaust and of course the 120mm rear exhaust.
Side fan really doesn't accomplish much.