Here's a quick update.
My Adelphos speakers have about 50 hours on them now. At lower listening levels or with female vocals and/or piano they sound wonderful. The midrange and high range sounds are crystal clear and a joy to listen to. At louder volumes, unfortunately, there is very noticeable resonance. I cheated on the cabinet and this is the result. It is an excellent and inexpensive lesson that physics can not be defeated. I will either buy a ready made cabinet from P/E or I will build a new one.
In the meantime, i will not turn up the volume too much and enjoy sweet music.