[Cathar]

I can say without a doubt that the BIX is holding you back.

Yeah, you mighta read on some site, heck even at HWLabs site who make the thing, that it will dissipate 919Wh of heat load.

What they DON'T tell you as what temperature the coolant is at when it's dissipating that heat load.

The answer, in my experience given some extremely powerful fans (no, I mean WAY more powerful than a 108CFM Sunon, or a 104CFM Panaflo H1A), is something in the order of a 50C rise above ambient for the water temps.

ie. At 919Wh heat dissipation, the BIX using fans WAY more powerful than yours, will allow the water to rise to about 75C in a 25C room.

A 172W peltier with a hot CPU under it will roughly be emitting around 300W of heat out the hot side, so expect water temps around 20C or so above room temperature using the fans you're using.

I'm very annoyed at the lack of adequate information supplied by HWLabs. It borders on misleading, and many people think the BIX is the dog's 'nads when it come to radiators, and it isn't. IMO, it's a middling-low performance radiator.

Go to DTek Customs and order yourself a pair of their 6x6x2 heater-cores with shrouds if you can't be bothered finding, buying and making up shrouds for some cores yourself. Two of these babies would come pretty close to what you need to handle the sort of heat load you're talking about.

Okay, so with a BIX your water temps are about 20C, or possibly more, above room temperature. Now the TEC will have a max temperature differential of around 65C. A Maze 2.1 will allow the hot side of the peltier to climb to about 5C above the water temp, so our cold side of the peltier will at best be about 40C below room temperature.

Throw in the cold-plate to cold-side thermal goop layer, and we lose maybe another 5C, so the opposing side of the cold-plate that touches the CPU will at best be about 35C below room temperature.

Now if we throw in the CPU thermal goop layer, and munge a bit for the thermal resistance of the cold-plate itself, and you'll probably find that the CPU can't get much below room temperature under load.

Not good.

....and the culprit here is the BIX.

Edit: Note the above discussion deals with temperatures only, of that I'm aware, and it does not take into account actual wattages and heat transfer, but the point here being to discuss what would be a theoretical minimum temperature that a TEC could take the CPU to if it were of sufficient wattage to dissipate the CPU's heat.