Look into getting an Optima battery. The CCA may be just a bit less, but they're not bothered as much by discharging from stupid stuff. I have one that is over 5 years old and has seen duty in a Jeep CJ-7, a ski boat, and now my Jetta. It'll spin the engine like it's a toy. (Note: avoid Optima batteries for cars with the battery under the back seat, as they don't have vent tube connections.)
Problems from storing batteries on concrete is a myth, and I've posted about it on this board before. There's an article somewhere on the
BatteriesPlus page about it. You can also buy an Optima from them.
If you choose the Mercedes-Benz brand battery, definitely call roadside assistance to get it. Several people have reported paying around $115 from r/a, but the dealership charged me $135 for the battery plus 1/2 hour labor to install it while the car was already in their shop for other work.