I agree, the Wondermega is awesome! Don't think I'll ever own one though due to their cost, but one can dream.
Re the Mega Drive, it does indeed have native RGB output and I utilise it as its composite output is horrible. If you don't have a scart TV, you can always use a scart to component transcoder and the results are wonderful.
I took some comparison shots a while ago, to illustrate the difference between composite and RGB on a Mega Drive.

^ This is on a scart TV, RGB on the left and composite on the right. Note how much more detail comes through in RGB, especially noticeable on the shop window in the background.
On a similar topic, even the Master System has native RGB output.
