For the 2SS with the options you listed, the MSRP quoted is correct. Here's what I come up with using GM's supplier pricing website:
MSRP $39,990
Supplier Price $38,633
USAA Incentive - 750
Sales Price $37,883
Sounds like you're getting a little more off than that ($3093 off MSRP). I think I would jump on that deal.
PS the website to look up supplier pricing is:
http://www.gm.com/vehicles/currentoffers/
Click on CREDIT UNION MEMBER DISCOUNT, then Price your vehicle. Select your options and it will give you MSRP and Preferred Pricing numbers