Well, I'm using a waterblock (Swiftech MWC-5000 w/adapter plate). I ended up ditching the retention frame, and purchasing a new metal backplate (the stock backplate uses push fittings. I needed the one with screw posts).
I know that's not the answer you are looking for though.
If you read that review where it showed the capacitors getting in the way of a stock HSF, there was an answer I read about it on a forum (somewhere..). It turns out that you can actually put the HSF on either way. If you mount it so the cam lever is oriented towards the bottom of the board, it doesn't interfere with the capacitors.