Re: New computer.... overkill maybe?
Why not wait and see what ATI crossover dual GPU set up is like before commiting with dual 7800's. You never know, it might turn out to be like the Radeon 9700 over the Geforce 4.
Also, with kit like that, what PSU are you considering on using. A good £70 looks in order.
Delta: "What's wrong Chris?? Chris: "I miss my old Cyrix"