I think one candidate should be Vandersteen. The model would depend on your willingness to buy used or new but look at both the 2 and 3 series. With their time/phase coherent and minimal diffraction designs, they can excel in imaging and soundstaging. Also, your generous room dimensions suggests they could be set up properly - distance from front and side walls being a key to maximizing imaging.
Their only drawback would be the lack of compatibility with your lower output amps (that some don't approve of the spartan appearance may not be a problem in your situation, particularly once you hear them). I would think a tube amp should be at least 50-60 wpc and that might only work best with the addition of the Vandy subwoofers (being self powered, they reduce the main power requirements).
Their only drawback would be the lack of compatibility with your lower output amps (that some don't approve of the spartan appearance may not be a problem in your situation, particularly once you hear them). I would think a tube amp should be at least 50-60 wpc and that might only work best with the addition of the Vandy subwoofers (being self powered, they reduce the main power requirements).