The normal running temp on a 20VT coupe is about 86 degrees or so and it should be up to that after about 10 minutes driving or about 5 or 6 miles. Some more info
here I would guess you're about 320bhp or so(?!) and I'm fairly sure others with similar spec to yours are using the standard OE thermostat with no temp problems/issues.
If you're worried about cooling temps whilst driving hard, you can get an uprated radiator made by Pro Alloy or Pace, but they are around £300 or so(I think).
As long as the fans kick in when they should and it warms up nice and quickly, I wouldn't worry about it too much. But if you're concerned, just buy a new thermostat for about £35 and a new expansion tank cap for about £6 or £9, but as far as I know, a different opening temp thermostat wouldn't be required.
Mark