Quadruple. Nice.
I suggested the M3 for a couple of reasons;
A. Almost everyone I know who has driven one considers it the gold standard for performance coupes, as close to the perfect "Drivers' car" as you can get for the price point.
B. You can get one with tons of different options. SMG, Manual, or Auto, lots of color combos, yada yada...
C. In his price range, it can be had BRAND NEW, warranty and all. A lot of the other cars suggested would be purchased used.
D. It has a respectable aftermarket, if he decides he wants to go that route.
E. It is comfortable enough to do pretty much anything he wants to do with it.
I cannot speak to the stylishness quotient. In my opinion, they look sexy, but only he can decide if he likes the looks of it.
If you are looking for someone to "talk you out of" a vette, my opinion is that vette drivers have a certain stereotype, and none of them fits you very well. You are educated, affluent, have a full head of hair, and are under 40 years old* (Vette guys, hate all you want, but you know I speak the truth) and honestly, there are tons of them on the road. Nothing about a vette is unique.
Of the original two, I would have gone GT-R.
*-I did not create the stereotype, I am merely aware of it. In much the same way that I am aware of the widely held opinion that no man that drives a "new" VW Beetle is anything but a tree-hugging, candyland skipping, friend of Dorothy. Of course, not ALL of them are, but really, is that something that you would knowingly embrace?