The only AMV's I consider high quality come from www.animemusicvideos.org, though you have to subscribe (freely) and you need to download them to watch them......
For example, here is a link to youtube to a neat video clip (1/3 of it actually since it's very long):
YouTube - Reflections of Style 3 (AMV) (1 of 3)
You can find this video clip in much higher quality on www.animemusicvideos.org if you look around a bit
P.S.: If you want to see it whole in youtube quality, I put it up in my profile.