I'm not sure how this will work since your speaker already has a "sub", of sorts. I'm going to go with a REL (Strata or Storm, maybe two) with my full range CLS's and still think it will be a tough match (i.e will the REL keep up with the speed of the CLS's, will the additional low frequency come at the expense of transparency ((I already know that the answer to this is "yes", but don't know how much I'll lose)). I'm not sure how a sub will match both your esl panel AND your dynamic woofer. Seems like there's going to a lot going on there. You have a very small panel as is (and there is a direct correlation between panel size and sound with Logans) so I wonder what the net effect will be. I've heard great things about REL -- the only way to go with esl's -- but you may be better off with a bigger Logan. REL's don't come cheap. Why not upgrade to a bigger panel and bigger woofer? SL3 or Ascent? Your net cost might be about the same with better results.