The Motif ES8 is indeed a heavy board (about 66 lbs) but instead of just glueing lead weights under the keys as many makers do, Yamaha provided a counter-balanced action system that feels better than any other board I know of. I'm sure if there was a way to keep the quality of the action and make it lighter then Yamaha would have, so I assume it's as light as it can be considering. I like having the best-quality keyboard for my studio centerpiece keyboard/controller, but my stage board has to be lighter so I use the 9000 Pro, which at 45 lbs is just about as much as I care to carry regularly. If I'd intended to use the Motif for regular gigging, I'd probably have sacrificed the action and a dozen keys and gone with the 76-note model.

On the power supply thing - some external power supplies create noise, and all of them are specialized for the keyboard they go to. Often they have a fairly high-amp output and you can damage the keyboard if you use a generic replacement. I once drove 25 miles to a gig only to find I had left the specialized Kurzweil keyboard power supply at home. Fortunately my wife brought it to me and all was saved, and I special-ordered an expensive spare. But I like it better now that all my keyboards, speakers, etc all use the same inexpensive and common power cord.