Dead battery in the E46 M3

[TD]

This is the second time in a couple of weeks that I've gone to take the M3 and found it dead. The last time I jumped it and (hoped?) that maybe we had just left something on by mistake. A second time would suggest that it's time...

So what's the latest recommended non-OE battery?

Our local BMW dealer quoted me $161.10 for the OE battery w/ CCA discount.

Batteries Plus, which used to sell the OE Douglass batteries but doesn't any more (which may be due to Douglass getting out of the business - their website no longer has any car batteries on it), suggests a Rayovac battery model (SLI48H6) that goes for $95.

Anything else I should consider? Given that the weather is going to be prime for the convertible tomorrow, I want to take care of this later today. Batteries Plus has the benefit of being a few miles from the house.

EDIT- Just called Batteries Plus... That one is not in stock but the guy I talked to said that, for the M3, he recommends a different model Rayovac (SLI94RH7) that goes for $149.99. I notice the DIN size is different between the two, so I also now need to figure out what will physically fit.