go for that a1200. that a600 is neat but very limited and got no aga.....
you should get this....
a1200, joystick, amiga mouse, composite/s-video cabel, aos3.1(and aos3.5/3.9 if needed)
ide2flashcard and a 1gb flash card for the hd
indivision for good display on your flat screen
an acceleration card blizzard 030 and 32mb ram or a blizzard 060 64mb ram or other 030/060 cards, 16mb is minimum
an pcmcia card reader that you can use flashcards with for easy transfer between the pc and amiga
an pcmcia network card for internett/network etc
an usb thingy for the clock port so you can connect a usb mouse/flashpen/extern hd/extern cdrom...
and some old floppies... always good to have a few, you never know when you need one..
if you need a sound card and can find a melody1200(then you also need a clock port expander), then you can play mp3 and do some more seriouse music making..
i think that pretty much cover it...