Should not be a problem for the vettes. Those are heavy cars.
Then again, those SRT8s are sedans and station wagons, not in the same class as a vette. Equally appropriate question is what the hell GM has that can even come close in that market segment? I see nothing. CTS-V or STS-V for a good $20,000+ more? GTO is a 400hp 2-door (not sure if you wish to say Subaru WRX-STi as a part of GM, at least I think they are). One rumor I heard is that GM killed their upcoming rear wheel drive platform in part because they could not build a competative model to DCs for the price. Hats off the DC, they saw the opportunity, and had the balls to capitalize. I drove the 340hp Magnum and 300, damn fine cars for the price!! You can get AWD as well, which is what I want for my wife's other car when we eventually trade in her Audi A6. I see nothing in the GM lineup that can compare, except for a $60,000 STS AWD. Very sad in my opinion.
I agree with the comment about the upcoming Mustang Shelby Cobra GT500. Will be a 2007 coming out next year. Latest talk is 5.4L with supercharger, intercooled at 8.5 psi. At minimum 450hp and with very cheap mods easily over 500. I know its not a vette, and I know what I am saying is blasphemy here, but my wife's 2003 Cobra convertible is an awesome 400hp car for $30,000 (was a brand new 03 I drove a hard bargian for). If the 2007 GT500 is as much improved as they say, and close to 100hp more, I'd get one in a minute for under $40,000 as Ford has continued to claim. I'll always have a vette though too, maybe a new Z06, maybe just my 99.
Sorry for the rant.