If u live in a warmer climate, I would DEFINTELY upgrade your cooling system (t-stat, fans, rad, etc.) Cheep insurance in the long run...

 

The hottest I have been able to get my coolant temps so far have been 215F. Thats on my modifry ECT gauge. I have a stock Rad, thermostat, and a 35/65 coolant/water mix. During the summer im gonna run water wetter to keep temps down.

 

I would say do the Tstat and fan switch no matter what.
Bringing head temp down, is great with boost, less chance of detonation due to higher head temps. Head cooler, equals more readiness to accept the heat created by extra HP.
This is a must IMO. ive done it to every s2k ive owned, and every one ive built, notice a trend.. all my cars and clients cars make more hp than everyone else, with same stuff or less?
do the cooling mods, you wont regret it.
As for larger rad, not needed unless your really pounding the car, say track days, or top speed runs in hot climates.
When you really lay on it, you get this big heat spike/curve, and the small ass stock radiator doesnt have the room for that accelerated expansion, so what happens... you have mad overflow and lose coolant. then you have a mess, and you need to top up before next run.
seen this happen.
Thats why the larger radiator (more capacity) is good, has room for growth of coolant.
Later dave

 

is there a 06+ aftermarket radiator yet?