Here is what I think of the comparison:
M6: A bueatiful and luxurious choice no doubt, plus its V10 is probably one of the most refined you'll ever drive. A very tempting offer indeed.
Porshe: Its main value is in its liveability, yet not in GT3 form, I wouldn't go for it.
Aston:Not a big fan of aston, and its understated look and unattractive interior are a negative point against it. Yet if your a real affectionado for these passionate vehicles, and the heratige they hold, go for it.
CLK: Mercedes sure has it going with the CLK, yet because of its timeless bueaty, it mey seem to some as oldfashoined, or stale looking. Although I surley beg to differ, I myself wouldn't get one consideering its hefty wieght and various steering problems. But still a good choice.
Jag: Truly the ugliest Jag I have ever laid eyes on, though its pretty powerful under the hood, it looks, feels and drives hevier than it really is. Plus its price is very unfair in preportion to the car itself.
R8: An extremly exotic, overwhelming and thrilling drive. Little to none can mach the brilliance wich is the Audi R8, a true sport tourer of the 21st century. But its a bit too low for my taste, and I would consider other more suitable options if i were to buy something that pricey...
Maserati: A choice made by only the "creme du la creme" of enthusiasts, breathtaking bueaty, sublime power and inspirational lavishness. Truly the only choice for the distinctive individual. If I had a 100,000 to throw, I'de surly dump it on the extraordinary Maserati GranTurismo.