Chrysin has only been shown to block estrogen conversion in vitro (lab settings), in people its questionable at best.
6-OXO - works so so, I've always noticed signs of increased test (oily skin, etc), but not much in terms of estrogen suppresion (water weight reduction, etc.)
Gaspari's Novadex is essentially 2 forms of a stronger type of the substance in 6-OXO. This and Rebound XT are good PCT supps. Make sure you're taking milk thistle, fish oil, and hawthorn berry to make sure your liver, BP and HDL are returning to normal.