The Thermaltake unit outputs 220W combined for the 3.3V and 5V rails. Assuming the rest of the 500W goes to the 12V rail, you get 280/12 ~= 23A. The Corsair unit can do 33A with its 12V rail. So the Corsair unit is indeed better.
That said, if you are not overclocking much I think 23A should be ok. If you can deal with the noise, $15 may be a good try.
The Model M is not for the faint of heart. You either like them or hate them.
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