The Amiga 1000/500 could be upgraded to support these things, but
in a pretty inelegant and clumsy way. They had to plug into the external
expansion port, and in a "train car" fashion, one device beside the other.
Even something as simple as memory expansion beyond the built-in 512K
RAM had to be added externally! Compare that to the IIGS, everything
could be internally added save for floppy drives and CD-ROM.
Amiga came out in '85 waaaay before the GS
The original Amiga came before, but not way before. The A1000 was
released July 1985, the Apple IIGS September 1986 (and while that's
only one year later, it doe in fact pre-date the Amiga 500 and 2000
by four months; those were the first usable Amiga's). :)
I'm sorry but a psuedo 8/16 bit machine was no match for the Amiga...
I'll admit, the Amiga had an edge (that's putting it lightly!) for
animation and multitasking, but otherwise there was much the
Apple IIGS had over it IMHO.
The IIGS Finder and GUI in general made Workbench look
a child's toy by comparison. The GS's Ensoniq synthesizer ran
circles around the 4-voice DAC in the Amiga. And its internal
expansion, via its 7 general purpose expansion slots, made it
a more opened and accessible system. It was a small thing,
but I also preferred the fact the Apple used a two (or three)
button analog joystick over the one button digital stick!