I had a problem with the cooling in general when I spiked this directly via the mainboard USB. The solution was to use the NNZXT

I used the Z63 with a 5950 for a few months. It depends on how much voltage your CPU needs. If only individual cores are boosted and the voltage is 1.45V, as it was for me, then the CPU heats up. In games, I have always cracked the 80°C mark briefly when loading or starting the game. That's the case with my CPU, I don't know what it looks like with yours. If all cores are used, the temperatures were between 64°C and just under 70°C.

I have now switched to a custom water cooling system, GPU and CPU are kept in check with two 360 radiators. When gaming, the CPU still rises briefly to over 70°C when something needs to be loaded, etc. If you have room for the Z73s, take them. It certainly won't do any harm ;)