Some of the more recent Sony remotes use a high-frequency IR band that isn't readable by the standard consumer-IR input of the empeg. Do you have an exact model number for that Sony remote so we can check?

Note that you can go into Hijack's "Button Codes Display" screen, and if the remote works with the empeg's IR sensor, you will see the values appear on the screen and can therefore create your own IR translation table, you don't need our help.

More information here and here.