MGadAllah, I assume that English is a second language for you. Mike has answered all of your questions in great detail. I suggest that you go back over what he was written as many times as necessary to understand it.

As far as the 286 and the 4600 are concerned, you're crazy to use both, but if you must, hook up the 286 the way he said and then hook up the 4600 as he instructed. The two have nothing to do with each other.

Mike goes way out of his way to help people get started, but you really do need to read and study the available materials to understand what he is saying. The Behringer manuals are not good, although you might want to download one for an older mixer, like the MX2642A (http://www.behringer.com/assets/MX2642A_P0019_M_EN.pdf). If that doesn't help, read one of the Mackie manuals. They're better for beginners.

Your QX1204USB mixer should do exactly what you want. If you insist on buying a new one, don't get the 1622. Get the one Mike recommended. He has a solid reason for every recommendation he makes.

I know he'll read this, but let me suggest that you not contact him with questions about the MDX 4600. If you do, his answer will be, "Don't use it." So, I saved you some time.