So, simply put, you have HC-300A in your CPU-only loop and are able to full stress your w3580 while the coolant temperature remains at 10C all the time? Is that it?)
How long is the stress test (in minutes/hours)? I suppose the compressor of HC-300A was 'on' all the time? What are the maximum temperature for the cores? Give some numbers now and supply those pictures later.
(I am eager to see a couple pictures of your entire loop)
I have attached some pics with temps. There is nothing special about this proc speed or vcore volts. I boot up at these settings then use an EVGA o/c utility to go higher after windows has booted.
Stock loop temp settles 2C above room temp at 26C, no load: Proc temps about 42C
Stock, after 153 seconds of wPrime 1024, loop temp has increased to 27.5C: Proc temps about 76C
Chiller set to 18C (18C loop temp): Proc temps about 29C
Chiller set to 18C, wPrime 1024: Proc temps about 64C
I think that is a VERY nice temp gain