I have an older pair of the L1290s, which are a little smaller and older than the M15s. I think that they are a great set of speakers for the money. I have since upgraded to another set of speakers, but I will never part with these ADS speakers. I'm not sure if it it was an actual upgrade or just a lateral move in another direction. If I purchase another home with room for another set of speakers, they will be going in that room. The speakers have a domed tweeter and a domed midrange. Some people say that the domed midrange is not as accurate or nuetral as it should be. I very much enjoy their sound. They are very easy to drive. I believe that they are above 90 db with an impedance that doesn't drop much below 8 ohms. I was driving them with an original B&K ST-140 with great success. They are bi-wire and bi-ampable. They are fuse protected. They have a good clean low end with excellent highs and mids. My 1290s do not have the same bottom end that your M15s will have. I have had many speakers over the years, but these have never given me one minute of grief. They are my perfect spare set of speakers. I have a set of KEF 104.2 and a pair of Platinum speakers that will be sold before I sell these ADS 1290s. If I were to trade in my 1290s it would be for a pair of 1590s or M15s. Jim