What do you mean by component video do you mean a single socket for the video or three sockets marked either as RGB or YPbPr (they are not the same though).
What make and model is the amp,as this would help a lot as someone may have a similar setup.
Have you tried the second socket on the amp, with another source. Try it with one you know that works on the first socket. That way you will know if its an input problem or a problem with the amp. On some amps you can configure the video outputs and sometimes the inputs say to PAL, SECAM or NTSC. If you get wavey lines or static it may be set to NTSC. Also check to see if there is a setting or switch to change from RGB or YPbPr.
Try the svideo out for the Wii and see if that helps.
Can't really be of much more help without knowing the make and model number of the amp