<<When I entered 0491 (aud) nothing happened>>

Then the code is not in your remote, if it was the LED would have flashed twice indicating that the code was accepted.

<<the remote seems to accept it but the power-off does not power off the AMP.>>

If the code really was accepted, was the power button the only button you tried?

<what are they.>>

Check my site.

Rob.
http://www.hifi-remote.com