You go boy!!!
When you say VT625 kit??? You mean VT 2 600?
This is a 6 psi kit and yes your stock clutch will be 100%. They run a 7psi race car and the clutch has held out pretty fine for 40k miles.
I would definitely go a 295 rear section tyre. Rims should be a 10,5J rear and a 9 J front with 255 section tyres. This is what I have and traction is still challenging, however pretty good considering the HP the ESS kit is putting down.
I have KWV3s and Brembos stability is unbelievable and stopping power 100% matched for the cars extra power.
Go Big or go home
check out these threads and you will see the traction with 295s dry roads and temps of 26 Deg C