Charlie,
The only thing I know about the Yamaha PAS system is what I've read on some other forums. No one provided glowing reports about the system, and in most instances, those that purchased the Yammies returned them to the dealers. Charlie, I suggest you purchase the Logitech system from Comp U.S. of another retailer with a liberal return policy, one that will not penalize you for returning the equipment if it cannot fit your needs. Let your ears make the decission for you. And, if you're married, let your wife's ears make the decission--they're better at this stuff than we are.

Cassp,
Have you tried the Logitech Z-5500 system? If so, I'm surprized at your comments about them.
With only one exception I know of, Scott Langholf, everyone loves the sound quality and the system's ability to provide excellent coverage over a broad venue for audiences to 150 people. I've used the Z-5500 with just the keyboard and mic, and with an Alesis Multimix 6FX mixer, fired a pair of guitars and two mics through it, plus the keyboard, and it kicked butt over any conventional system I've used in the past 20 years--including my big Peavey's that I spent a small fortune on.
The key to using them is proper tuning of the keyboard's EQs, Mic EQs and setting the volumes correctly. When this is done, the entire spectrum of sounds is transmitted beautifully through those tiny speakers and subwoofer. Naturally, speaker placement has a lot to do with the dispersion of sound, just as it does with any other system. If the speakers are not positioned correctly, sound quality and coverage will obviously suffer.
Good luck,
Gary
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Travlin' Easy