This sure sounds like the old NTSC <> PAL problem. Been there.
When I had an A1200, I used a Commodore 1942 multisync with it. It's a great setup, IF you can find one. I also used an NEC Mutisync 3D with the A1200. It's only 13" but has an excellent display. You can get 800x600 with the Super 72 driver (might have to tweak it a bit with Mon-ed).
