The 500 is sheer classic of course, but it's pretty hard to find expansions for it.
Well, so far, yes. But soon, there will be plenty of expansions to choose

Most powerful of all - the Zeus cannon

50 MHz CPU with RAM, IDE and RTC.
Also there will be Jens' ACA500 with 14MHz CPU 2MB RAM, CF connector, and a A1200 edge connector, so you can further add A1200 expansions.
And you can actually buy Kipper's super affordable 8MB RAM expansion right now.
So I'd say things are looking pretty well for the A500
