ALL lcd tv upscale the picture to display it in full screen.
Upscaling does'nt make the picture better.
Resolution of the the Wii's outputs stays the same, it's just a scaled image to get it onto a flatpanel fullscreen.
So why would you want to have an upscaler? is the image of your Wii displayed as a small cubic?
If not, your image is scaled allready.
It could well be that your TV has bad scaling abilities, resulting NOT in a bad image BUT in a noticable lag.
THEN it would a good idea to get a good scaler to scale the image ( not resolution ) before sending the signal to your TV.
HDMI Key is only handy if you want to connect your Wii through HDMI. This has NO advantages as to the image quality when using Component cable connection. ( resolutions stays the same Image is scaled the same way. )