Before buying that modulator, I want to know how does it perform with today HDTVs, because I have an old pong and the image quality this way is very crappy.
No need to be hyper crisp, but has to render GBI at 3x zoom clean enough to be readable/playable.
I would love to find someone with a pal system in a pal region to confirm that colors, especially, renders fine (in France, and most Europe countries, we had Pal consoles, although TV broadcast was in SECAM.

We may also start a topic about playing multiple source on one big screen if you know other options, that doesn't cost $1000 or more (like HDMI multiplexers). If it's the case, maybe the topic would be better in the General/Gaming section.