Hrmm. Why would you necessarily want it on the webhost instead of on the shoutcast server? does your host not support the intro file?
Or are you saying that you want to make a playlist with:
2. Relay 1, 2, & 3?
If so, just make that playlist in winamp, save it then post it on your site. Of course, use the add URL option in winamp for everything and don't drag and drop it for maximum results.
Then tell your listeners to click that playlist to listen. Thats all i could imagine. I don't think the shoutcast DNAS supports off-server intro files. i could be wrong tho.
I Make. Perform. Mix. Play. Music.