Lee,
I believe the tiptronic is a bit like an auto box, but with a gearlever that you can 'override' the auto changes.
I guess you could also call it a 'clutchless' manual box. Either ways my personal view is that it would be very unusual in a 40.
I'm told that 911 (types) can be very scary if the box decides to change gear mid corner!
Perhaps the G50/60 would be a better option.