[LensLarque]

The absolute best for 'old systems' is Micomsoft's XRGB-3, but it's now rare and quite expensive.
But the HD Box Pro units are said to be a good (and cheap) alternative.

And yeah they're right, buying a good used CRT tv is still the best thing to do I think. If you can find one that's been manufactured around 2000-2006, there's a good chance that it will still work nicely for maybe 10-15 years.

 

[LensLarque]

I recently found a 29" 4:3 Sony Trinitron Wega in very good condition (w/ scart RGB of course ). The babe wheighs 49Kg but wow, its so much better for all the old consoles and my supergun.

The only annoying thing is that of course, most 'used but still in good condition' CRT tvs have flat tubes, wich very often have bad geometry (esp the big ones) and need a lot of complicated tuning if one doesn't like a distorded picture.
Finding one with a curved tube and in good condition is best, but quite rare now...