The line input would be huge, so I didn't have to use an outboard harmonizer to get the guitar, trax and vocals all through the monitor speakers. This is old news .... we've said it all before, right?
Dave, I have two inputs on my PA80 . When working in school music classes I would have my mic in one of the inputs and my guitar in the other. Does the PA 900 not have the same? God Bless, Don