RAM 150 which includes an 8" ABR or for even more bass, the RAM 200 with a 10" ABR. Both are larger than the 15xr but both are vastly superior in every department. Another contender would be Goodmans Achromat Sigma although difficult to find now. They also sport a 10" ABR and have loads of bass although the cabinet finish may not be to everyone's tastes...Finally, B & W DM 14/1400 which are quite compact considering they use 2 x 8" units and provide more accurate bass than all of the aforementioned.