im in your same position. i started a thread a while ago, i hope it can help you. and i hope maybe someone else can give us some more info :o
i aint too sure but i know it would enable the 480p mode in the Wii options with the HDTV component cables. plug them into that and get an HDTV VGA cable to be sure your gettin the full quality it can display. altho it may not make a difference because of the switch. im thinkin of buying this item myself just waitin a little for money and some more advice.
also from another post on this forum(vga box vs vga box), heres 2 links of similar or the exact same items:
http://www.mayflash.com/vgabox/pc029/pc029-1.htm <-- this item i think is the same as the one i was lookin at on Ebay. maybe different box shape. this is what you want.
http://www.mayflash.com/vgabox/vga001/vga001.htm <-- VGA input to Component output (much more expensive and prolly not what you need).