Firstly, I would advise against buying a second hand VGA monitor anyway, cos they can blow anytime!
What I did was made a cable for a Hitachi telly that also had a RGB port. Picture clarity is excellent and flicker is reduced in all interlaced modes, it still flickers, but you can still work with.
Make the caple yourself - cut of the last two pins of a 25pin cable (carefully) it works fine. The socket on the back of the telly was 7 pin DIN. Only needed 5 pins so used a 5 pin DIN!
I have tried it myself, just using a SCART telly might be better!
Get 3.1 if you're going to use Amiga sensibly, its much 'nicer' datatypes etc etc.