Just sold the PSR2000 so I am left with the yamaha P-80, S-90 to come (or perhaps the new MOTIF rack). I utilize a Mackie DFX-12 Mixer and EV SXA-100 speakers. Awesome sound, great Vocal clarity. I also utilize a Mackie 1501 Subwoofer when I do the DJ thing. 300-400 people with the EV's?. Nothin to it. But it depends on the room, set-up and what you're playing. The EV's and the Sub are fine playing CD's for dancing. Just the keyboard and vocals appear to be fine too, but I never crank it much during dinner and cocktail hour. Good Luck Brian