Frankie,
I believe there are members who were somewhat disappointed with their Behringer mixers - I am not saying that it's bad, but with some of the units having problems (if I recall correctly, it was the excessive noise), you should listen to the unit you are buying, or else make sure you can return it without a penalty (and be ready to pay for shipping).
In general, if an arranger keyboard is a part of your setup. you should look for a stereo mixer (which will allow you to pan the right and left outputs to the different sides). I don't believe that Yorkville is stereo, and if I recall correctly, it has dual mono amps. which allow you to to have separate volume control over the same mono signal (which may be useful to drive the mains and the monitors, but provides no stereo separation). The Mackie 808S (and I think some high-end Yamahas) have three amps built in - two for the two sides of stereo mains, and the third for the monitors, which are usually mono anyway.
I have been using a Samson D8B stereo mixer, which has 8 stereo channels, and a built-in Zoom effect processor. I am leaning towards a more scalable setup, and am putting it up for sale. If you are interested, please e-mail me privately.
Regards,
Alex
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Regards,
Alex