@Sim085
As you can see, there are lots of good opinions here.
Basically, you have two decisions to make. One is what do you want to do with your Amiga. The other is how much money do you want to spend.
"... what I could actually do with such an Amiga?"
In its day, the classic Amiga was a good all around general purpose home computer. There were word processing programs, spreadsheet programs, paint programs, music generation programs, and games. IMHO, it was already what we would now call a multimedia computer. Some Amigas were used for commercial applications. The NewTek Video Toaster created a niche market for the A2000 in broadcast video production and started the desktop video revolution. Some people have A4000T machines with Video Toaster 4000.
These days, those programs are harder to find.
"... is it possible to do most of the things I already do with a PC?"
The answer depends on what you want to do.
It is very important to remember that the classic Amiga machines and most of the earlier software came out years before WindowsXP and the modern PC hardware we have now. Most of the Amiga hardware is frozen in time, although some newer add-on cards are available for USB and ethernet connections. If you are currently using a PC with WindowsXP or Vista, then there are probably lots of things you take for granted with the software and hardware. You may have become accustomed to doing things a certain way with the PC hardware and software.
Many things we do on a PC can be done on an Amiga, using a different program or a different method or more than one step to get the job done.
So, for example, can I print my Word document that I created on the PC at work or school with my Amiga at home? No, not directly. But if you saved it in Rich Text Format (RTF) format, you may still be able to use Final Writer 97 to open the document and print it.
Another example, can I surf the net with my Amiga? Yes, if you have the correct add-on cards and software. Some web pages look different when rendered using an Amiga web browser.
Back in the day, I would surf the internet over dial-up modem at 19.2 Kbps with my A2000HD, running AmigaOS 3.1, AmiTCP/IP, ppp.device and Amiga Mosaic or AWeb. I did not have an accelerator card, so it was slow. But it worked and I was amazed. My machine had 1 MByte ChipRAM, 4 MBytes FastRAM, a 40 MByte harddrive and a CD-ROM drive. I used FTPMount to download programs. I had SMTPpost to post email and AmiPOP to retrieve email, but I was dithering over which email reader to use. I wrote a simple text only sendmail type program (in ARexx). My ISP did not support Amiga. I was on my own.
Now, back to you ...
You have your A500+. If I understand correctly, it is still a good game machine for non-AGA games. Back in the day, the A500 was a very popular model. Many people maxed out their A500 machines with a harddrive and accelerator. Not sure what parts are still available these days. Not sure if there are add-on parts for USB and network connections. Serial dial-up internet connections are still available in some areas. I recommend an accelerator and lots of RAM for any network activities.
As the others have said, "as new" A1200 machines are in stock again because a bunch of Amiga Technologies A1200 machines built several years ago during the Escom days have became available. Amigakit also sells refurbished machines. A1200 was and still seems to be a very popular model. If I understand correctly, it is also a good game machine for games using the AGA chipset. Apparently, it is easier to obtain expansion cards and kits for the A1200. Again, I recommend an accelerator and lots of RAM for any network activities.
There are also the other machines, the A2000, A2000HD, A2500, A3000D, A3000T, A4000D and A4000T. These all have separate keyboards and expansion slots inside the system case.
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redfox