Hertz did for a while. Otherwise your best bet is to call the rental facility to ask for a price match.

As for the Aveo. The Cobalt has lately been priced at the same. (not sure if you'd call it an upgrade. I called it purgatory myself.) There's a chance that the location would be out of that class of car and would put you into a Cruz/Focus. I've rented a Cobalt and been upgrade all the way upto a CTS.

For a fairly strong guarantee you could get the Chase Continental Presidental Plus Mastercard, its not cheap but includes lounge access and a few other things. There are minimum car sizes though. http://www.avis.com/car-rental/html/.../co/index.html