Interstate, Optima and Die Hard (among others) all make AGM batteries. I would see what consumer reports says and go from there

 

My 2009 CTS battery was on the right side of the trunk and easy to change with everything done thru a single access panel. My 2014 is on the left side and a real pain to change requiring access panel removal, back trunk panel removal, rear trunk trim piece removal, floor panel removal and finally small access door removal on side back of trunk on battery side. I did not use an AGM and find no problems. I use Advance Auto [ Autocraft Gold size H-6] where one can get a 20% off coupon online if patient and the battery is not an emergency. The battery is then shipped to store and you will be sure to get a fresh on [still check date]. Advance will install the battery for free. I called them first to verify this knowing the pain in the butt it is to change in a '14 and that they will not do some battery under seat models. They said yes but Advance allows 1/2 hour and I know why. Worked fine for me at around $159 less core.

 

I used an Autocraft AGM H7 wich is made by Johnson Controls. Top of the line at Advance and I got it on sale and in addition another 20%. off. Cost me less that $160. No problems except PIA to replace.

 

Exact same battery here. great price & quality.

 

You guys did very well paying less than $160 for that AGM. It is usually $40 more than the H6 before any discounts. And to be fair I forgot to subtract the discount from my quote above which would have made the H6 $137.