I use a PSR900 and a Motif Rack ES. It seems to work fine. Some sounds are better than others but that is to be expected. I also connect my Fantom X8 and it also works fine. With all of that I use different speakers for each board. I use a Traynor K4 and Yamaha MS50 and sub for the Fantom. then the sound module is thru Roland Cube 30 monitors and Samson Resolv 65a with a sub. The PSR900 is thru onboard speakers and the Cube 30's..... I also have expansion cards in both the Fantom and the Rack ES. Overall it sounds really good... Hope this helps.... Good Luck