It really depends on how your desk is set up, but honestly, any of the OB offerings are going to the same size or larger than the XLS, and will likely be at least 15"-16" deep, and will need at least 3 feet from the wall behind them, only exception being the NX Studio, but is also taller and deeper than the X-LS.
If you want something smaller, there's always the A/V1, and there should be some new drivers for the LGK kits on the way within the next month or so that you might want to consider.