alms, you're right, Porsche's are expensive when compared to their counterparts. In fact, per unit, Porsche is the single most profitable mass produced car out there. However, to a degree, I am in the camp of you get what you pay for. While it costs more, I like the way you can customize the interior on a Porsche. I do like the aftermarket pictures of the Z06 seats and dash you show. That definitely looks like the way to go with the vette. As far as the Porsche not inspiring as much confidence as the Vette, try a GT3 or RS 911, not just a regular one. They've done wonders with the handling and aerodynamics on those cars--even with the "rear engine bias". My GT3 felt just as comfortable above 120 as any Corvette I've driven. The Vettes, to me, start feeling nervous in triple digit speeds. If you want a truly stable car well into the triple digits, the Italians have that covered--for a price. I also agree with you about the Cayman and Boxster. If they put a 450hp engine in that platform, what a car we would have on our hands. Of course, they won't intrude on their halo car's territory--too bad.
As far as the GTR goes, a loaded Z06 now costs more than the GTR premium. See the comparo in last month's Car and Driver. And for the money, it is a fantastic car and one I'm seriously considering.
At the end of the day, we both agree buy what you want. As I said before, the Corvette is the best bang for your buck sports car. While I prefer the Porsche or a Lambo, I am proud that the Americans can make cars of this caliber and believe they are and have been on the comeback. The 5.0 is also evidence of this. The Germans should be taking heed and will need to continuously improve their products and provide better value for the dollar or they may risk losing sales.