Hi and welcome,
As some people said, get yourself a cheap, used a1200 computer. It is quite powerful (compared to other amigas) as standard and can be rather cheaply expanded, though the ultimate expansions with PCI slots and what not makes it somewhat expensive.
You can pick up dirt cheap stock a1200's. I suggest you start out with that, find out how you like it, eventually buying some cheap expansions for it (accelerators, harddrive, NIC, etc), and then deciding if you want to be a part of the "future" as well, and go with either the official AmigaOne/AmigaOS4 solution or the similar Pegasos/MorphOS system.
One thing you will notice, is that people will try to drag you into either the amigaos or the morphos camp. Get that stock a1200 and decide for yourself where you want to be.
IMO
Sincerely,
-Kenneth Straarup.
