500+ h/p, 650+ torque, my car became a complete joke on street tires.. Fun, to an extent, but at times down right scarey.
Now, after knowing what I do.. for a daily driven street car, as my 01 GT will be.. I have a goal of 350RWHP through a 100% stock 4.6 single turbo, and will be content keeping it that way.. IMO 400-450rwhp, or close to it, should be enough to keep anyone happy.
Right before tearing my car down, I was close to or at 600rwhp, and I could not imgine anything more being 'fun" on plublic streets, especially when the car just wants to lose it at any speed, in any gear. I will say running around town on slicks made the car more predictable, but who wants to do that... At the track, yes more would usefull.. Really depends on if it'll be a track, or street terror.