I got my SRT at 20. Started power-adders at 21 and haven't stopped. Responsibility is the key issue here. Irresponsible teens will get into trouble no matter what they drive; fact is that all cars are capable of speeding. Take my brother, for instance. He wrapped a 94 Civic sedan with maybe 100 hp around a huge oak tree. Now, it can certainly be argued that a more powerful car would have hit the tree harder; but, again, a responsible driver that knows his/her own limits as well as those of the car would not be in that situation in the first place.
I'd say do what it takes to get what you want. If an SRT has caught your eye, make it happen!
If you do get it (I hope you do) I suggest doing what I did when I got my newest motorcycle; approach it with the assumption that it will kick your a$$ if you mistreat or under estimate it.
Start slow and reserved, slowly pick up the pace.
Good luck.
PS. Stay away from the Sprint Booster for now, That almost got me in trouble when I installed this weekend