Do I use it to emulate computers and consoles ? Not really, but I have set it up to emulate some of those systems. I have found that it is only worth using when no other good option exists which is rare outside of the obscure systems that have very few to no emulators for it.
I have always just used regular rom downloads, never used the software list stuff.
Based on what you listed here I would suggest using WinUAE or FS-UAE for Amiga, Vice for C64, Stella for Atari 2600 and Kat5200 for Atari 800.