It sounds like you’ve never been pleased with the bass with just main speakers in that room. When I moved into a large room, the bass completely disappeared. 2 subs are especially important in a large room and I got the best results by placing them on either side of the room, about halfway front to back but slightly staggered, and facing to the rear behind furniture. Less interference with the mains but still provided that fullness which had always been missing. Why not keep your 2 subs with your mains running full range? Then play with your sub xovers to get the right fill.
Another big improvement in bass quality and quantity came when I placed 2’x4’ acoustic treatments behind the mains and soffit traps stood up on end to the sides of the mains to reduce boundary interference. In a large room with the speakers well away from walls, the boundary interference will be deep into the bass. I used GIK acoustics which won’t break the bank. The soffit traps are placed to control boundary interference from both the mains and the subs. My bass is pretty awesome now. Good luck!