I personally like the EK waterblock and if I were ever to get 2x 3870x2's to hook up to my swiftech system then that's what I'd use.

I imagine that 2 MCW60s would fit on a 3870x2, as I have then on my 3870 and they arent that big. From looking at the picture, I am 90% confident they'll fit, as they only take up the space in between the 4 screw holes.