I use the mClassic for console and PC gaming (cheap 4K TV, PC only powerful enough for 720p/1080p). This is Marseille's latest version of the upscaler in their mCables. I really like the effect (smoother edges, but kinda painted-looking and with some halos where there's strong contrast), but it's clearly not the same as actually higher-resolution content. You might find an mCable cheaper, but there are many variations (Gaming, Cinema, Ultra? &c.) out there, which perform slightly differently, so check which model you're getting.
You are going to see more of a difference if your screen is a higher resolution than the content e.g. vWii's 480p or most Wii U games' 720p on a 1080p or 1440p screen.