I am fortunate to have a 996tt cab. Don't have the X50 and it does have tiptronic. Two completely different cars. TT is car that does not require a drivers complete attention. Great cruiser, and very relaxing and can bring it on when it has to against 95% of the ricky racers that always seem to want a piece of me. Mines been to 167 on the way to Vegas kicking a SL55's butt from a 40mph start. My wife loves driving it, top down to the post office, hairdresser, girl friends, etc. MSRP was $138K. Only thing I did was put a set of Gemballa's on it. It is truly a beautiful car.
For just a little less money (by the time all the mods are done)the Viper is the most open top, or closed for that matter, fun I have had in a very long time. Nasty, aggressive and just as much an attention getter, possibly more w/the Corsa. Other open top exotics just get even more expensive and will not have any better fit and finish of either car I already own. That being said, I will be adding an open top Murci or Superamerica because I have been fortunate and want to have one. My expectations are that my 2005 SRT10 w/paxton and all the good go stuff including a traction control system will still be the nastiest, bad boy of my group and most fun to drive. And, for some reason, modifying it and taking it to the strip makes more sense than any of the other exotics one could own.
They are all fun, but for now my Viper rules. If one is allowed only one car there are two choices in my mind; a stock Viper vert or a 997 6sp cabriolet of comparable $. I have owned 20+ Corvettes in my life and still have a 66 427 roadster (of course). Corvettes and the typical vette owner got boring as hell starting with the c-3's.
Don't even worry about the occassional c6 z06 you may spy stalking you. The Viper stock w/exhaust is much more car and fun. Intimidate the guy by threatening to kick his ass and move on.