Beam to Ultra, in my opinion.
Depends on what you want to achieve, music or surround sound for movies.
If it's music, then the optimal solution would probably be 2x Era 300 set up for stereo and connect a Sub. (You deactivate the front speaker when set up as surround) However, they spread the sound much better than your SL even if set up as surround. Will therefore also give a better sound image in your setup than SL.
For movies, I would go for Ultra, but you should be aware of how it is placed and preferably a little away from where you sit and watch TV as it needs some space to "shoot" the sound out in various directions before you get the optimal experience. Ultra also handles music well, but that's not its strength in my opinion.
A good mix of music and movies, then I would go for Ultra.