Earthquake actually makes some fantastic subwoofers. They are not a household name, but I’ve spent time in their booths several times at Cedia shows. They are usually the ones that are loud and raucous..maybe not as well refined as some other vendors, but I don’t think that’s their style. The 15” that you mentioned is a beast of a subwoofer too. I know that a well respected member on AVS wrote his experiences with that subwoofer some time ago (including measurements)...so possibly search for that. Of course all the normal recommended Hsu, Svs, Psa, Rythmik, etc. are all top notch products as well. However if they are not readily available for you, I wouldn’t be leary of Earthquake products at all. Just my .002