If you want a "scalpel" instead of a "broadsword" The Opel Speedster, fully tuned only has about 330 Hp. But what a wonderful way to use 330 HP! It is small enough to be really agile on narrow tracks (Like Monaco) and with proper tweaking of the gerarbox it is quite fast. It will never be the first choice on tracks with super long straight-aways (the Test Course, GVS).
As for the EVO (If, like me, you LIKE "broadswords"). Try both the 6 and the 7. As I said, The 6(RS) is the lightest. I just have more seat time in the 7. You can make the 6 as quick as the 7 with gearbox tweekage. (A lot of the really awesome cars come into their own with tweekage of the gearbox). I prefer the way the 7 handles. But you may prefer the 6.
Some other cars that fit the bill for a 500 HP beast. The Supra RZ. IT is quite heavy, but it is a nice drive until you crack the 600 HP barrier. Then it becomes an intractable beast.
Either of the Newer RX-7s or the RX-8. I prefer the looks of the RX-7's. They are quite fast and handle well. But the RX-8 has lapped consistently faster for me.
Don't overlook the Viper. With stock gearing, (It think it has a 3.09 final drive, with the "sports-wide" slider set for about a 350 mph top end) it is an embarrasingly slow car. After full race tranny tweaks and the final drive to 4.44, let's just say it isn't the same car. Test the car on the track of your choice. If the car can't get nearly to the top of sixth gear by the 3/4 point of the longest straight, Go back to tranny settings and move the "sports-wide" slider 2 points to the left. Now go back and retest, setting that slider back 2 clicks, until you are happy with what should now (with your zealous tweekage) be awesome acceleration.
