I have tried two different aquarium style water chillers. The first was peltier based and more or less didn't work for jack. If you read the fine print on most peltier based aquarium water chillers you will see that they state they will not go below amby. So the coolworks ice probe is out of the question. As for the other chiller, it may work if it can handle the heat load. What kind of BTU rating do these have? I have an aqua logic CC25 unit that keeps my mobile at around 10C. The unit is rated for 1500 BTU's. I would reccomend a unit with a higher rating then this one. Many people around here are also making chillers out of AC units. This might be a goud way to go as these can be obtained for under $100.
One other thing to consider is that you will have to bypass the aquarium temp control unit so that it will stay on all the time. In most cases the temp controller on these units is limited to just above freezing if not higher. For my unit I run it 24/7 with not temp control. The thing I like best about my chiller is that it doesn't consume too much power. Being at -40 would be nice and all, but when that power bill comes in the mail, it's no longer any fun.
Oh, I like the pics! Nice work.