I agree with Gil.
I bought the Delta version of what he displayed for round $99. I used 80 grit on the disk and 120 on the belt. (After searching for a picture, I'm not sure Delta makes the unit I have any longer.) Buy a bunch of extra belts and disks. If you ever touch a piece of steal to the belts, pitch them. You don't want to push steel into your pieces of aluminum that you sand on next.
After cutting a chunk of aluminum on the band saw I would smooth it down on the belt and then take it to my 12" Delta drill press where I would have the scotch bright wheel mounted.
Easy access to the scotch bright wheel when mounted in the drill press and you can slow it down vs. the high speeds you see when mounted in a bench grinder.
While I'm pontificating, here is the list of power tools I used:
1) 14" 3 wheel band saw. (Paid $10 for it at a garage sale. Real POS but worked fine for cutting thin aluminum.)
2) Bench sander described above (About $100)
3) 12" Bench top drill press (About $200)
4) Bench grinder (Gift, no idea how much. DO NOT EVER use aluminum on a bench grinder. Do a search if you need to know why.)
5) Small chop saw as described on Dan's site. (Didn't use it often but it was worth the money)
Two things:
First, you will never have all the tools you need so just start building! Second, when you catch yourself saying, I can make THIS tool work even tough it is not the right tool for the job. STOP! Order the proper tool. Otherwise you will find yourself ordering the correct tool AND a replacement part. Just ask me how I know.