The sail panel speakers (next to the rear seats) are 6.5 inch subs part number 9365799.
The hatch component speakers (in the hatch area behind the rear seats) are 4 inch mid bass and 1 inch tweeters. The 4 inch are part number 16259011 and the tweeters are part number 16229091
You can get prices from www.gmpartsdirect.com
or your local dealer. Don't forget to include the cost of shipping when comparing prices - I've heard that gmpartsdirect charges a lot for shipping.