I don't know anyone with 4 digit HP numbers... 1000+ HP on the street is pretty useless, It's more about bragging rights than anything. I hope your buddies are planning big braking power and some suspension/chassis work as well...
I just want 400 HP to the ground and still be able to drive my car on a 5 - 7 hour trip to visit my family
Two points:
1. With 400 hp and 3.73 gears my Mustang is rather loud. I went through 6 or 7 different exhaust setups looking to reduce the noise level. Even with Dynomax super turbos it still is louder than I'd want it to be at highway speeds. 5-7 hour trip may get on my nerves.
2. If I drive it that long, I'm definitely going to stop at gas stations more than once.