Very similar,
Yes the Stingray will take you around town nice and fast, drop top and all, very nice! (X3)
The Z06 will relocate your eyes to the sides of your head... Want, WANT NOW!! (X5)
Like the X3/X5, cost increases proportionately.
I have the X3 but never heard the X5. Is the sound difference that great? I mean big enough difference to justify the price difference..I've read some peoples comments that they didn't think it was better enough for the price and that the scroll wheel seemed loose.