If the room is reflective you may not need much. Many public rooms are very reflective. If you are teaching/training and are the main person talking, you will need even less. I remember back in elementary school when they would show videos that it was just the TV on a cart brought in and it's speaker blaring. It was enough volume for a large reflective classroom.
Fortunately, that leaves you with many options. One I can think of are the large Bluetooth soundbars. Sounds like you want two, one left, one right. You should consider putting your money into speakers with many drivers (speakers) or lots of power.
Many drivers helps increase the amount of sound. Similar drivers next to each other reinforce each other 3db which is like doubling amplifier power. More power let's you turn the volume up louder without it sounding like a clock radio.
Speaking of which you could buy active speakers. If you crave sound quality more is the
NHT SuperPower for $200 each. It is active and is based on one of the best small speakers. Otherwise try your nearest Guitar Center or Sam Ash for their active PA speakers.