Well my 10kg bag is roughly the size of a child's beanbag chair (not the really big ones). So I guess the 20kg size would be like two of those on top of each other
If you have a spare room it sounds ideal - it might not look very glamorous but I used to put a throw over ours (so it looked like a beanbag chair
). And once you've used it to fill a cage base the first time it goes down in size a bit anyway.