B', I have the Godspeed and it seems to tune really well. Another guy Scott Seigel tuned in Atl whose SN on WISTI is Trey also has it. So as far as catless pipes go we know that one isn't a creeping problem. Faded has the Invida and it seems like a nice piece too.
You are correct to stay away from the HKS, unless going with an EWG, then it is a great cost saver.