I have cut outs on the gtx and NEVER bolt the caps on them, have had many cops tell me how nice it sounds. I worried about it when i first got it but not any more.
I have a pair of Stainless Works T-304 stainless turbo mufflers that a buddy put on his car, started it and decided it wasn't loud enough and took them off. He paid like $160 ea. If your interested in them pm me. Shipping would prob be a killer tho.
Don't think I'd spend the extra to get mandrel bends on the exhaust for my stock /6. JMO Doubt it would have a noticeable effect on my car anyway. Not sure of what the exact price difference is though.