Well, I have an idea for Kent's answer to no 2 about a potental rival car for the NSX, namley the NSX-R. The Chevrolet Corvette Z06 (00)
Now this might seam a miss-match given the weight and BHP differnces between both cars, not to mention I'm prob not the most quallifed driver (although I can handle most road and race cars if not all of them... can't say all of them becuase I haven't driven all of them...without TCS, ASM, on normal to sport and racing tires and with the DFP or even the DS2) and the fact the only places I have driven them HARD on N2 spec tires (only, have I have not tested them much on N3's or any other tires for the matter), are Laguna Seca, Infeneon Raceway, Autum Ring full, and Suzuka Full. I've driven them both around the ring but that was months ago, and well, Suzuka and Laguna are the only real places I've driven then back to back on the same day, hard as I could, really Suzuka as that's a personal favorite track of mine and a proving ground for comparing cars besides Tsukaba and Infeneon.
From what I can tell you of the cars, and why I consider them worth comparing and in a way rivals are these reasons.
For one, it's their overall performace on the track regardless of how different these cars are. The vette has about 105bhp differnece (offically, the gap is most likley lower given the listing on GT mode has the car as 310bhp for the NSX) from the NSX, and the NSX is some 200kg lighter than the Vette. But it's because of their similar lap times first around Laguna seca...
The Vette got 1.44.427, the NSX-R, 1.44.375. Just to give you an idea, a GTR 34 I tested... I think the 1999 V-Spec II or something of the matter (there is a difference between them all), I got 1.46.607. All of them on N2 tires, all of them with no TCS, ASM, and using the DFP. Laguna is a track I'm used to from many other games, this being little different. Plus I'm most familar with the vette, I got that time on my first lap, took me a few more to get the NSX's time, I can't help but think I could work harder. But then we go to Suzuka where I have worked hard on both cars...
The NSX-R, 2.27.255, which was a lot faster compiared to the last time I drove it within the 2.34 second range when I had first played GTR. The 2.27 time is my latest, quickest time yet with it. But the Vette Z06...was 2.26.928.
Laguna Seca gives some power difference but at the same time a sense of control and agility with your car, not to mention you have to commit to a number of corners, you can't slack off espically on the uphill sectors of the track. Far as Confidnece goes with the Vette, it's very high for me. Suzuka is a similar case, though the power difference make itself obvious in a number of parts, but also just how the overall package of each car comes together as well.
As for the Vette..
This car dosen't under or oversteer too much when you it thru a corner right, and the elevation makes little difference besides to be more carefull on braking going downhill, not so much an issue uphill save for some corners. In real life the vette is a bit more tail happy, which GT3 did actually nail almost right. This Corvette in GT4 is not so tail happy, but it beats severe understeering, espically when you can learn how to kick the tail out the right way with this car. Not to mention it's one of the fater normal road cars I've tried for a very long time, the throttle response, the brakes, it all works to make it a very confident track car

.
I just wish they made it sound more like the vette in real life... but I hope they'll get it right for GT5 (that and getting the new C6 and Z06, no excuse at this point, same for the TVR Sagaris while where at it...).
It overall gives me a sense of confidence to race and to do time attacks more so than any other car. Which for me might be a bit biased becuase I've driven this car more than most others including the Imprezas, the Lan evos, the Skylines, etc. So of cousre I'm going to specilaize more in that area, even with the Evo's which do feel on one end more planted on the road, on another not the handling I'd like, a similar case with the Imprezas and Skylines (and out of all of them... I'm actuall an Impreza fan..and the only Evo's I really like in terms of handling so far are the Evo 3 and Evo 7... ).
Alhough the NSX is different in a lot of ways, such as feeling different from the Z06, it's equaly as quick around most tracks as the Z06. It's weight difference to an extent can be felt as much as you could with a DFP as it feels lighter and a bit more nimble around corners. It's got everything you could want except for the power, but even with what power it's got, it's very quick around corners. It's a superb machine.
With the NSX, I feel a tiny bit more confdience driving it, and a bit more of a thritll besides the fact if you treat it the wrong way or provoke it into oversteer, you either do it right with this car, or it back fires on you baddly. It's otherwise very level and very easy to control. So easy you can stay on it's limits, and if you keep at it, you can be very fast against cars far more powerfull than this one which includes the Z06.
What I also like about this car is how it seams to feel very much like the other NSX's including the Acura US model which I also like a lot... becuase both feel very similar even with the power and weight differneces and what have you. The American spec model is not as fast but it does fell as confident and as abled as the full blown Japanse model, then again the NSX-R is to the NSX lineup what the CSL and GTR are to the M3, and same for the Z06 to the C5 models. A high performace hardcore or track derived vehicle, lighter, more powerfull, more race prepaired.
That's my reason anyway, I'd state more but I think I'll just ramble on and on... don't know if this is even usefull information anyway till I get a reply... so I'll just wait for one.
Till later.