If this lump does have 500+ bhp you need to look seriously at an alternative gear box or accept you may well break the standard one eventually, which is a pita because it is quite a piece of work to replace it.

Personally I really would like to ditch the standard box and fit a six speed sequential unit.

I saw one being operated by steering wheel paddles a while ago with the gear lever moving in unison on its own that looked rather nifty!