I also have this question. Specifically about the GSP since they are the cheapest. They look like "name Brand" Chinese replicas (As most if not all godspeed products are) of the Eagle rods. I'm told the Eagle rods require machining on some blocks and Eagle's reply is "that's just the way it goes sometimes". Issue being due to subaru block casting tolerance differences.
I was told Brian Crowler rods are good, and around the same price as eagle.