I'd only get a MKII if you were needing it for general photography as well and budget was limited, or you didn't want extra computers and camera power supplies when out on location.
As Doug said, trying to cool a DSLR is an expensive and tricky operation, and you won't get low noise levels like a dedicated cooled CCD camera will give. A 5D MKII is still fairly pricey, it gets you up into dedicated CCD territory price-wise.
I can't comment on the Taks themselves, I don't know enough about them.
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