My car makes just a little less 650 hp and I'm going to be honest with you: it can be exhausting to drive on the street. Don't get me wrong - I enjoy driving it, but with the cam required to get the ponies around 600 hp, 4.10 gears, a loose converter (I know yours isn't an auto), and a reverse manual valve body, I get worn out just driving the thing to the gas station (which I do a lot ).
...and don't think that you don't need to upgrade a lot of other stuff too when you get over the 500 hp mark. Feets has a good point when he suggests thinking about turbos.
As the San Angelo drag strip recently closed (see the thread in the race section), my car is now a "street only" car, and a really hard to drive one at that!