Well the question is what you really want to do with your "new" "Amiga" ?
If your into games and apps from yesteryears (Win)UAE is your way to go.
If you want to experience a "modern Amiga" you should imform yourself a bit more into detail.
Testing OS4 is next to impossible without handing out $$$, you might want to visit a local user meeting (is such thing exist).
Testing MorphOS can be done quiet easily and cheap:
Buy a supported Mac:
- eMacs and PowerMacs can be had for 50Euro or less
- MacMinis are bit more expensive, if you do go that route searching for the "silent upgrade" model with 1.5GHz and 64MB VRAM is strongly advised.
MorphOS runs unregistered on these for 30 minutes after each boot before it will slow down.
If you like it you can invest 111Euro into a licence.
If you don't like it you can resell that Mac through the same channels you got it and get back more or less what you paid yourself.
Edith:
Neither MorphOS nor OS4 offer "true Amiga" feeling, both reimplement the API on PPC-CPUs and come with an emulator to run 68k-SW.
SW that bypasses the systems or relies on specific features of the orginal chipsets (aka real Amigas) won't run unless you put them inside an UAE-setup. Pretty much all games fall into this category.
(Win)UAE only emulates an 68k, PPC OSes like OS4.x or MorphOS won't run here.