The current Amiga computers (or clones) are standard PPC computers (just like Apple Macs) that don't have any custom chips anymore.
That's why you'll have to make an important decision first, *then* pick the system of your choice:
If you're intersted in developing and using up-to-date (*cough*) applications, playing today's games (the few that are available), browsing the net etc. you should buy a NextGen Amiga. Disadvantage: Doesn't have custom chips and won't run old games or very old applications. Will run most of the stuff you remember from 1997/98 just fine though (basically, everything that supports gfx and sound cards will work on these machines).
If you want to play old games watch old demos, stick with a classic (AGA) Amiga. Upgrade it with a 68030 CPU, some fast RAM and a HD. Disadvantages: Hideously expensive to upgrade, stops working if it doesn't like the color of your socks, feels slow no matter how much money you spent on upgrades and won't run newer versions of the OS (unless you're willing to sell your car to buy a PPC accellerator).
The next generation Amiga is called "AmigaOne", and is distributed by Eyetech. It currently comes with the pre-release version of AmigaOS 4.0 (incomplete beta version with GCC based dev kit), full version of AmigaOS 4 is scheduled for release sometime later this year. Now go and check the A1 prices. If they don't make you run away, come back here to get more info ;-)
http://www.intuitionbase.com is a good source for information regarding the A1 and OS4.
An alternative to the A1 would be the
Pegasos. It's a PPC based motherboard, pretty similar to the A1. It's a lot cheaper, but it doesn't run AmigaOS. It runs
MorphOS, an AmigaOS clone that can run AmigaOS 3.x applications (just like AmigaOS 4).
MorphOS will not run AmigaOS 4 programs, neither will MorphOS software work on AmigaOS 4. MorphOS will not run on Eyetech's AmigaOne and AmigaOS 4 will not run on the Pegasos.
Therefore, your options are:
- upgrading a classic Amiga
- AmigaOne with AmigaOS 4
- Pegasos with MorphOS