I am quite sure that just like the PSR 740, you will be able to use the line outs and the internal speakers at the same time. The speakers are rated at twice the power as the PSR 740. We'll see how much more volume is produced. With the PSR 740, I almost always bring some monitors to make the music more footstomping loud for the old folks. I have two sets of monitors that I use. I have some Numark M-40 monitors, 20 watts per channel, very good sounding, and pretty light. I put these in a duffle bag. I lay the duffle bag in front of my keyboard, I pull down the duffle bag around the speakers and I plug the speakers in. When I'm done with the show, I just pull up the duffle bag around the monitors and throw the cables inside. It's very quick way to get extra volume with a minimum time expenditure. I also own a set of Audix PH15 studio monitors, 45 watts per channel. They're just a little louder than the Numarks, about 10lbs heavier, but they sound superb! I find that in this business it's good to have two of everything, because you never know when something's going to break.