Depends on your budget, I'd say.
You might also be after a cheap IDE solution for your A500.
Check out
http://amiga.resource.cx for some example (there are other websites as well).
If you have a Turboboard with an 68020 or 68030 or plan to get one 8highly recommended!) I'd give a serious thought to the A500 clockport adaptor, which gives the A500 two clockports. With these clockports you can get a so-called "Subway" USB interface and get a cardreader via USB.
Or you might go for a Busboard, which enables you to use Zorro (II) Cards, like the Algor, which gives you USB as well. I'd recommend getting a different case, then, though.
Just a matter of your budget...
Have fun,
McTrinsic