Well, for one thing, I ALWAYS play stereo. That's what the keyboards are designed for, and most phase cancellation issues have more to do with collapsing less than perfect stereo samples to mono than the PA they are played through.

It is INCREDIBLY difficult to get a good stereo piano multi-sample to sound consistent when collapsed to mono. Not only do you have phase problems, but different phase problems for each and every sample in the set. Unfortunately, few arranger manufacturers (if any) provide a matching set of mono samples of their best piano sound, but force you to use inferior, older mono piano sounds. NOT what I bought the keyboard for, exactly!

And yes, unfortunately, I DO play at fairly high volumes to cover a large outdoors area (one of my house gigs), and certainly wouldn't want a PA that spread that volume around consistently! The only thing that keeps my ears from damage is that we set up BEHIND the PA, as do most conventional systems, and use lower volume monitors for ourselves.

I personally think for high volumes, having the PA be the monitors too is a huge disadvantage.

I have a friend that had a PAS system, it's not like I've never heard or used one.... And I thought for low to mid volumes, it was quite good, though a little lacking in the low to mid-low range (he only had one sub). Nice typical Bose clarity at the top, but not warm enough for me....

For the typical OMB, this might be just the ticket, but our main PA often has to deal with a full REAL band at close to concert levels, as well as my duo (and I do have a smaller rig for small parties, just use the JBL SRX top cabs from the main PA, a Mackie sub and small Yamaha self-powered mixer) so unfortunately, the PAS's just don't meet my needs. But they are cool....!