Getting back to thw ISIS,for a moment,as I just spoke to the folks at Avalon,it seems that the ISIS is a ported design.Though I'm sure it IS superb,the porting(regardless of mfgr claims)is NOT as accurate in the midbass and bass as a sealed enclosure.I have never heard a ported box that did not have a signature sound.I have heard ALL contenders,like the big JM Labs,biggest NOLA Exotica(deep bass,discontinuous),Wilsons etc.If you have heard a really great sealed enclosure you know what I mean(provided it does the rest of the musical spectrum well).
I have a friend who has held onto his old Infinity RS-1b's,and "mega modded" them.These are sealed box speakers,and when you hear the pitch definition in the lower octaves,that they possess,you are simply bowled over.I really believe,due to the shift in the speaker design industry,to ports which satisfy the average consumer,that it will be an educational experience for any of us to hear a great sealed box design.Sorry for the run-on sentence!
BTW-If I ever own the ISIS,Id happily rationalize these comments!!
Best!