Sti block and WRX heads? Use .051" thick COMETIC head gaskets for a 8.5:1 CR. If you use the OEM Sti gaskets you'll get a 9.17:1 CR. Also, you can use the RS head gasket and get something like 8.8:1. The last one I'm not 100% sure.
With the OEM gaskets you will have to watch boost/timing as your CR will take the place of the higher boost levels. I was running abour 18-19psi on my VF22(stock pistons)
With the .051" Cometics I can run up to 22 psi as my CR is lower now. I had to retune the map completely.