Post your results if you go higher, I'll follow with interest. I got mine to 2.25 on an a7v8x-x - temps were lower though with an sk-7 and ys adjustable fan.
Do you feel you have any headroom in your overclock? If not, I don't know about spending the money on another hsf.
Maybe bring it up to what you can do on higher temps and benchmark it; if it's stable but the temps are unsatisfactory then it's time to upgrade, what do you think?