After looking at the many demos and list of features of the SX-900, I'm very confident that it would be more than adequate for anyone performing on stage - you just have to familiarize yourself with the tools and USE them. I am amazed at the number of individual players that did not take advantage of the Music Finder Directory feature on earlier models. It was a fantastic asset for on stage performers, and completely eliminated dead time between songs, but if, and only if, you used it properly. And, when used in combination with registrations, a performer could very easily transition from one song to another with zero dead time. Navigation on the SX-900 seems very easy to me, but I have tutored others that could not navigate easily using any operating system of any manufacturer. To some, the task of navigating from one song to the next was very perplexing to say the least.
Several years ago, I posted a video on this very subject. I'll see if I can find it and post it again - it may prove beneficial, even for SX-900 users.
All the best,
Gary

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PSR-S950, TC Helicon Harmony-M, Digitech VR, Samson Q7, Sennheiser E855, Custom Console, and lots of other silly stuff!
K+E=W (Knowledge Plus Experience = Wisdom.)