If you tower your A1200 and add a Mediator then you can use cheap 2nd hand 1MB or 2MB ViRGE cards which (In my experience) worked just as good as my Cybervision643D.
Also, if you get an Indivision AGA you can have some large screen modes or even widescreen. The speed isn't impressive compared to RTG and you're limited to 256 colours, but it is better than nothing.
