If you are looking at just getting into Amiga. The most common application for it is retro-gaming. I'd recommend an accelerated A1200 with hard drive and a license of WHDLoad for that. (I'd also buy a new AGA flixer fixer for it from AmigaKit so you can use a modern VGA display.)
Using an Amiga as your primary machine versus a cheap modern PC is not likely to be the experience you'd expect.
As for what is the best Amiga - I'd say the A3000+ prototype A3000 with AGA, of course it was never mass produced.
