Welcome back
What happened around 96-2000 with the Amiga was just a rollercoaster of letdowns.
Right now there are a few "Amiga Next-Gen" around, using a completely different architecture (PowerPC) and only compatible with the old ones via emulation.
Most of the people on here are pro-Classics, but there are a few specialized forums for NG. The most famous example of a newly produced NG is probably the X1000 with its hefty price tag
On the classic side, the Amiga is still alive and kicking (at least in terms of expansions)! You have new products coming steadily from Individual Computers (scandoublers, accelerators, network cards!), like the ACA500 you named.
If you mainly want to play with your Amiga, you could go the WHDLoad way - you install everything on HD, and the game loads entirely from there. No more floppies and less loading (I like the floppies though) - but you will need an expansion for that. The ACA500 should do nicely. You can also stick an A1200 accelerator to it to make the ultimate A500
Well, see you around