The Dayton Ultimax drivers are very good. I think it could keep up with the ULS-15, with enough amplification. I wouldn't be surprised if it had a bit more xmax and a lower Fs, so it should be able to dig a bit deeper. However, it is not the most sensitive driver, so you will need to give it adequate amplification. I would want to use at least 800 watts per driver. They will be fine with less, of course, and still get loud, but I don't think they will be able to surpass the mid bass performance of the ULS subs with less, if they can surpass them at all above 50 Hz. The ULS is a very nicely balanced sub in terms of performance.