Late reply, hopefully you'll see or maybe it will help someone else.
For legacy systems, "optimal picture quality" isn't going to be to use a an upscaler and an HD TV. It is going to be by using a Sony Trinition CRT (consumer or pro model, or other Pro RGB sets by other compnaies) and SCART/RGB. For the Sega Genesis, model 1, you can get a SCART adapter for it. Then you need an additional SCART to RGB or component adapter. That to the TV will give you a better video quality than using an upscaler, even Micomsofts' XRGB kits. For teh Genesis, the SCART/RGB adapter combo will run at most $80, but finding a proper Set may be a more difficult task. If you decide to go the route of CRT, I would recommend 19-20" set due to weight but if you're Atlas you can go for the big ones. Also, you need to make sure that whatever furniture you put the set onto can withstand the weight. Modern home entertainment furniture can be quite flimsy.
I can't say about the Super Nintendo.