I like to hear my arranger in stereo...most of it's effects are stereo based, and I have a lot of styles wherein the instruments use stereo delay or hard panning, so I miss those enhancements when using a mono system. When I was demoing arrangers, Yamaha insisted I use a stereo system.

By far the best system I have personally used in stereo was two Bose L1 Model 1's (the bigger system and each had a sub woofer) when I was doing some work in a theater setting...it was amazing how the stereo separation seemed to work even at quite a distance from the stage. I realize they are very expensive, and I was only renting them, but the sound was killer and coverage was outstanding.

I did try two Bose Compacts, but in a large hall across the street from the music store, and got the same great response in stereo and wonderful coverage, but, of course, they weren't nearly as loud. Still, one could do a reasonably sized room with them...and a major benefit is you don't need the extra cost of a monitor system.

Again, these Compacts are pricey, especially in pairs, but my old Yamaha MS-60S powered monitors, (which I still use) were around $800 each nearly 25 years ago, and I don't regret spending the extra bit for good reliable sound (Bose weren't makin' the L1's back then). Thing is, you may buy several arrangers over the years, but a good sound system needs only to be purchased once.

But, it's your money and just my humble opinion. Good luck.

Ian