Getting to 5.3 GHz on air is a distinct possibility and if I were into setting records then I would take the motherboard out of the PC Case and install it on a test bench, remove a couple of sticks of RAM, add another cooler to the Noctua and have a couple of desktop fans blowing air over the whole thing. But I think I will call it a day at 5.2 GHz as I don't really want to go through all that at the present time. And it's worth remembering that the 5.2 GHz I have achieved is with my PC configured as it is for everyday use, which I feel makes it even more impressive.
Yes, switching to water cooling would be the next logical step if I wanted to run 24/7 at 5.0GHz+ and I believe the system would allow me to do that. As I mentioned previously I am now seriously considering this option and feel that when finances allow, a water cooling system will be my next major investment.
The main reason I wanted to tweak this system and to see what it was capable of was because I switched after more than 10 years of running AMD systems to Intel. I also felt happy with AMD as the platform always allowed me a reasonable O/C but this Intel rig has blown my AMD system away.