Wow! Stock wheels are 23.6 lbs and chrome wheels are 24.6. Those are already very light wheels! Nice job, Pontiac.
The A/X wheels are 21.5 lb, so there is no compelling reason to get them in order to reduce unsprung weight. Track folks may be compelled, but I'll never notice the difference in performance or ride comfort between the stock wheels and the A/X wheels.
That said, I still love the look of them and that deep dish rim and I still want them.

And while not a huge difference, losing 10 lbs of unsprung weight is a move in the right direction anyway.
This really says more about how seriously Pontiac sweated every aspect of Solstice performance. I assumed the OEM wheels would be cheaper and heavier than they are, but they are already lighter than most of the "light weight" 18x8 wheels shown on Tire Rack. The more I learn about the Solstice, the more impressed I am about the uncompromising performance. Sweet!
Oh, and thanks LOADS for pointing me to the information I needed. That was as fast and easy as could be. The people on this forum are amazing. THANKS!