maybe magictv is a good thing for u ? i used this when i had no gfx card...but only 16 colors wb then...., hmm or was it 32....i dont remeber..sorry.
should be on aminet.
(atleast then NO flicker)
pps:mediator is a good choice , if u want a normal a1200 pci version then u should check amibench.com etc for second hand stuff (might be cheap) ... but i would say...go for sx model...
hmmm and i am pretty sure i used 800x600 on my old amiga microvitec monitor.... check for screenmode hacks on aminet...