I have been working on putting a stellar hd+ in an xbox, but there is so many things wrong with that console I had to shelve it for my own sanity. I also recently got pixelfx's retro gem for a PS2, but I haven't had a chance to actually install it yet and it's an internal mod like the hd+. It looks like pixelfx also has a seperate upscaler called the morph4k though, that might be worth checking out.

Honestly, I didn't know that upscalers like that existed but now I'll have to check them out for myself too