A500+, 600 and 1200 (ECS and AGA chipsets) are switchable between 50/60 Hz. A500 (OCS) is fixed.
That sounds good. I was thinking of going for a 600 or 1200 myself, even though the 500 is the "classic" model.
Personally, I have an A500 (KS 1.2) for all those games that take advantage of the bugs (er... features,) of the earlier OCS & KS1.2 model. I have an A2000 with dual kickstart 1.3 & 2.0 for the ECS games and such. The 1.3 is the earliest that supported HDD boot, and there were quite a few games that came out for 2.0. Also, most of the really good utilities & such just work so much better under 2.0. Finally I have an A4000 for the AGA support and the latest OS (KS 3.1 & WB 3.9.)
The A500 is currently packed away because I just don't have room right now to set it up. Also, I'm trying to get a hold of a flicker fixer (scan doubler,) for it, but those are extremely expensive 🙁 I'm also planning to get a mouse adapter for it. The Individual Computers one (don't remember the name,) is the best I've found so far. Thinking about getting one for my C128 and Atari ST (if I ever get one,) as well.
The A4000 is still in pieces. I got a hold of a used tower case for it, and a battery replacement that I prefer (the previous owner had already moved the leak susceptible one off the board.) I just have to put it all together, and re-solder the battery connection (that will need some help, though.)
The A2000 is the only one I currently have connected up and running. I still plan to get an accelerator for it, preferably one that can be switched off with Icon controls. Just like with the PC, some older games have problems with faster systems.
If you are not wanting to get so many different systems, then the A1200 may be the route for you. It is generally more available than the A4000, but if you want desktop/tower conversion, be prepared for a lot of work. You can get a system degrader disk (free from many sources, though you will have to pay for the KS images,) to allow you to play most everything. You "may" run into a problem with OCS/ECS games and the AGA chipset. I just don't know if the degrader will actually allow that or not. I do know that some games choke on the wrong chipsets. Since my A4000 is in pieces, I cannot test it out. At worst, you might want to go with an A600 and A1200. Personally, I prefer the A2000 & A4000, but that's just me.