Well since the OP appears to be MIA.
Actually both the contact freezer and dark knight are so close in stock performance it doesn't matter which one you go with as far as the OP is concerned he just needs to decide what he's really after looks or performance.
Even though the Zalman he listed looks good it is far from the best performer and the already listed review tests prove that.
However its limitations should be the biggest negative in even considering investing money in it and I'm speaking of the internally mounted Zalman specific fan, it completely kills your fan swap choice options.
Zalman is finally stepping away from that looped heatpipe idea with their recent release of the CNPS10X Extreme, but they are unfortunately presently way behind the performance 8 ball.
If I was intending to spend the Zalman's cost range in money I'd be getting the Thermalright 120 Extreme with 2 120mm fans, however it would be a lot cheaper to go with either the CCF or the Xiggy HDT line.
I have a Xiggy the original S-1283 cooling my setup, however it surely isn't stock as far as Xigmatek is concerned, the heatsink base has been lapped and she is sporting 2 120mm fans one as intake one as exhaust, those modds increased the cooling performance by 10C.
Pretty impressive for a 30+ dollar cooler but it did take some work to get it there, I already had the additional 120mm fans on hand so they're not included in the price, but that is a factor too.
Warning: Anyone lapping a HDT type cooler, you better know what you're doing and when to stop or you can cut the copper pipe walls too thin.
Well thats my 2 cents guys. Ryan