Apogee GT

how restrictive is Swiftech Apogee GT Waterblock?

my loop is a black ice xtreme II x-flow rad , apogee gt, dd cpx1 pump

You can read up on the GT flow rates here
http://martin.skinneelabs.com/

And compare to other blocks on the web page, and compare more here.
http://www.skinneelabs.com/

I don't know per say, but all you need to know in comparison is found on these two sites.

BTW, your flow rates would be fine. As long as you don't have 10+ ft of tubing. I used the GT, was great in it's day.