i've got 450 front and 350 back. For road use it's just too much... I just cant go past 100mph it scares the hell out of me. Uk roads are better but even so... On the other hand, driving it on a track is just an incredible feeling. It feels very, very sharp.
I'de recon 350 front and 180 back, like KSA-Cossie said, would be a very good compromise.