thinking about it, if i calmed down on my "to the max" ideas :-) and actually spent some time sorting just one machine out software wise, some of the other posts reminded me that, most amiga software is very happy with one or two megs of ram. and going back to the day, how i would have killed just for a hard disk for monkey island2 or ledgend of kyrandia :-D
the A1200 seems to be the best for basic expansion.
you can find accelerators/ram cards with little to no fuss.
internal IDE for cheap hard disks.
and a PCMCIA port for network cards/compact flash adapters for easy copy files from PC.
and of course, their relatively ubiquitous availability.
otherwise, asking people here for "the best amiga" will lead to a variety of opinions :-D