The only new vehicle that I'm aware of that runs the fan right off the engine is the Dakota, but I don't know of any cars as of yet.

As for the Charger vs. 300C SRT-8 versions, they are within the margin of error with each other, but in the 0-60 times it seems that the 300 might be slightly faster but that could have been from other factors (such as the weather on the days that they were tested as I have yet to see an example of the two of them being placed against each other).

I would say you could very easily get an R/T up to the performance standards of the SRTs for the cost difference between the two, the only thing that you will have to remember is your upgrades will not make it as valuable as a SRT will be years down the road even if it is faster since an SRT is a more exclusive package.