My battery suddenly seems unable to hold a charge, and in two bouts of single digit temps it wouldn't start. Never had a problem before. What model battery is best and what could I expect to pay?

diehard has been very good to me and there between 80 to 100 depending on the amps you get. also would go with recomended amps

This is the one for your car and one of the best aftermarket you can buy.

From Car Batteries Reviews: "Many users at MySears.com and Sears.com say their DieHard Gold batteries have lasted nine, 10 or even 12 years, surpassing their original estimated life span. As with all of the brands, there are complaints of batteries lasting fewer than three years, though there are fewer comments about DieHard Gold than about other batteries". Me personally my battery in my truck is 10 yrs old and has never 1 time not started from a dead battery or needed a jump in any condition. hope this helps

Not sure where you are but in the UK the best replacement for the original Panasonic is a Westco which are highly rated over here & I believe are imported from America

I remember the Miata intro article 25 years ago that said that sometimes even in normal temps the batty would lose it's charge overnight enough so as to need a boost/jump in the morning to get started. I've remembered that all these 25 years.