My mate has a VXR Nurburgring. He has spent around £4k with Courtney Sport to have Stage 4 and more put on it and its about now about 350BHP. Thats with a whole load of uprated parts including turbo, intercooler, inlet and loads of other parts.
Its quick but he can't pull away from my Cupra R which is APR stage 1+ (made 360/350)
So i've spent £1k (£3k less) to get slightly more power, torque is about the same.
Can't remember what exhaust he has on his but its very very loud on full throttle and as you say it pops, bangs, burbles and spits flames at every opportunity when giving it some. Pretty sure he said it was on the car from new.
Both cars have uprated clutches but he also killed the gearbox at 50k miles. Its not driver hard all the time, just the odd run like most people. He is mid 30's like myself and although we are still petrol heads we are not young kids abusing the cars. Apparently its common enough for the VXR to eat gearboxes??
I'm contemplating a sports cat downpipe and stage 2+ software to see how much more I can get.
Would like to try and stick with the oe system if its not too restrictive.... subtle, quiet but functional

Might even treat it to a new FMIC (although the current one is coping just fine so far!)
His next move is LSD and handling mods. He doesn't want to go further power wise.
So I guess it will depend on the car and what level of tune it has. As well as weight and if both drivers are equal, tyres etc etc etc