"The only way to currently keep cab sims on in the XLR and of in the Outputs To Amp is to use the Amp out option."
that's what i actually did but it doesn't work... also I saw a youtube avid video about the live setting and the guy says clearly that nothing will be affected on the xlr outputs...here's the link .I did like scenario 3 and it changed also the sound on the PA!
http://www.youtube.com/watch?v=0tPgAtQ_i4A