The Mac would probably not get used too often, maybe a few times a month. I like to keep the Macs in working order before I put them on the collection shelf, in case I do want to use one or get parts from it.

From what you said, I think general purpose or low-ESR would do the job fine. Probably no need to up the voltage for how I will be using them (sitting on a shelf, fired up once a week or month just to keep the parts moving smoothly).