Another thing to consider is that while WHDLoad does work on 68000 machines like the 500 and 600, I've run into a couple of installs that use tools that don't work on less than an '020 (can't recall which at the moment, though) and the occasional game that just won't work (while it did on the 1200.) That, and with 1.5mb of RAM the Minimig is not ideal for multi-floppy games, and you'll also miss out on the few good AGA games that are around.
If you intended to spend that kind of money, a 1200 wouldn't be out of reach and would do way more for you.
As for CompactFlash, I'm using 4gb CF cards on one of my 1200s and in my 500 and they work very well.