The brick style power supplies for the Amiga 500/600/1200 are all quite weak. They're quite fine for bare systems, but it's possible to overload them once you start upgrading. (The difference between the A500 and A1200 power supplies isn't very much either.. It might work okay or might start failing after a while.)
A couple options (if you need something even bigger) would be finding a Big Foot power supply or hacking a AT power supply to work on an Amiga (just a matter of changing connectors.)
