Welcome Pubbrewer!
Your room size, depending on how loud you want to go, would seem to be more of a application for professional sound reinforcement application than home audio systems. And performers will have higher voltage balanced (XLR) connections anyway. I'd talk with companies like Sweetwater (they are excellent to work with) to get ideas. Having your own system has advantages (like having a master power/volume control at the bar and performers could travel lighter) and disadvantages (each performer would want to tweak it to their unique sound and the mixing board would have to be able to accommodate the maximum number of instruments, so some overkill would be needed).
