You will find a lot less options in the 451 size (and will you brakes still marry with larger diameter rims?), but there are plenty of choices in the 406 size. What distances are you planning on covering and what is the terrain like?
In terms of puncture resistance, the Marathon Plus would be hard to beat.
I have just fitted Conti Contact Sports (28/406). Apart from being difficult to seat on the rims, they roll well and the carcass is a lot tougher than the similarly sized Stelvios. Good for fast commuting on fairly even surfaces.
Last edited by Fear&Trembling; 04-03-06 at 03:37 AM.