I think the best reference I could give that you could relate to is Apple MAC. Moderen Amiga OS is hardware dependant on 68k and PPC processors, with the exception of the AROS development project mentioned above. AROS is a project devoted to porting the classic Amiga OS to x86 and other hardware, but it's still being developed. Though we here agree Amiga is one of our favs, it's really not your best choice for the latest and greatest 3D engine games (Yet).:-) To run Amiga OS you will have to buy amiga hardware. You can download the latest AROS port and run it on your x86 PC, but software will be a bit foreign to you and won't include the lastest port of HL2 or DOOM3

But don't let me put you off. Find and old amiga on ebay or play with AROS or even look up UAE (Universal Amiga Emulator) and emulate an amiga on your PC, I think you'll have fun anyway. Have a pocketpc? Then look here too....
PocketPC_UAE Amiga Emulator. Then just come back and ask lots of questions.
Plaz