Dirtstyle

@Dirtstyle
 

just buy a chiller, but be careful with condensation when you go deeper then ambient temperature.

Same basic concept in principal.

The fridge would have to be running all the time (which most dont because that is loud).
Otherwise it would be cooling stronger, but not more efficiently.
If one would go that far it would probably better to build a custom system for cooling with a fluid like in the fridge (I wont go into details here).
EDIT:
not more efficient because you have another part to power, the cooling itself would be amplified

It's certainly been done before. I doubt that a mini fridge would cool the loop enough to make condensation a problem, but that's and easy insulation fix if you do see it occuring. Only pursue this if you're looking for a fun modding project, otherwise is is somewhat impractical. I'm not one to judge though, I zip tied a cpu AIO onto my gpu once, and it worked quite nicely.

If only there was a OC Formula for the X399

That is 4.4 on a single core. 
 
Threadripper 2 will have slightly higher OC limit that Ryzen 2. So about 4.3 ghz. 
 
It will be 10-15% worse in gaming, depening on resolution and games it will be identical or slightly worse. It will offer a lote more computing power in heavily threaded loads.

then you will be happy about TR