Need a very good water block

[storm-chaser]

I have a heatkiller IV all copper waterblock at the moment. It is a great water block but very restrictive. I have three pumps, one before and two after the restriction which provides enough flow but the pumps are working harder than they should be. I want to remove the heatkiller and find something on par, but yet slightly less restrictive so I can continue to have good flow through the loop.

This rig is used specifically for cold weather benching, and I am running 40% methanol as coolant. Any suggestions?