If you're not going to run the audio with the engine off...then any battery that starts the vehicle You really don't need any of those gel cells or anything else unless your going into extreme temperatures. Otherwise, they're just trendy.
OP stated that -20 is a possibility during the winters in his area... I'd call that a tad bit outside of conventional.
1978 F250 2wd (460 c.i.d. / C6)- soon to give up the powerplant to an '80-'86 F150
White 2000 Grand Prix GT coupe One still slow and loud... other one scoots just a bit.