Building a beasty later on and a good dependable DD now I veiw as mutually unattainable. Once you have funds to make it a beast it'll be beat to death from normal everyday driving. So I veiw it as.
1. buy the 6er it'll be fun take remaining funds put into either savings or into a dedicated project car.
2. Buy a gt to have fun with.
3. buy a cheap DD that's cheap on gas too and build a beast.
4.You said you want to beat vettes and camaro's well take the $ you have and go get a LS1 camaro.
Just to add, I can guarantee you that's a conservative tune on stock heads and cam. Probably stock mid-pipe as well. 11 psi should throw a mostly stock 99-04 to the 330 range with a more aggressive tune. Add a mid pipe and a pair of heads and a cam, and you've got a lot more power than most would expect. As for prices for parts, since everyone is convinced the V6 is a pos motor, parts are really cheap, too. I don't know, personally, I'd take the six because I could give a damn about all the panty dropping factors and what other peoples opinions of my car would be. I'd take the car that already has forced induction on it and work it from there. You could probably even get him to sell it for cheap.