I too have tried REL subs (as well as many others)- and I could not get them integrated - in fact, they sounded the best when they were unplugged. If you ask Wilson Benesch about subwoofers, they will most likely tell you what they told me, "Subwoofers are evil". I didn't believe it at first but I do now. One of the many benefits to using Wilson Benesch speakers is how seamless they sound - adding a subwoofer seems to introduce nothing but problems.
If you go with a sub, make it a Velodyne HGS - 12" or smaller and try to find a home for it in-between your speakers or the midrange & soundstage will get too distorted. The volume will need to be set very low and the crossover must be set to the minimum (40Hz) or use an external crossover set between 33 and 37Hz depending on your room for better integration.
If you go with a sub, make it a Velodyne HGS - 12" or smaller and try to find a home for it in-between your speakers or the midrange & soundstage will get too distorted. The volume will need to be set very low and the crossover must be set to the minimum (40Hz) or use an external crossover set between 33 and 37Hz depending on your room for better integration.