muddy base

I have a new question about muddy base performance. I am pretty sure it is a function of the room etc, but here are the detail. I have CDX/82+flatcap(I know, I know, I need Hicap), 180, on a metal spiked rack with meadowlark Kestrals. In my old apt. I had lots of problems with positioning the speakers and reflections. With the first set-up, the low end sounded AMAZING, very tight slamming base when needed. Unfortunately it was in a hot spot, and the trebles were incredibally shrill. I moved my whole apt. around,putting the speakers in front of windows, and found the highs sounded good, but at the expense of the base, which was now muddy, almost distorted. I figured it was the low ceilings or the cheap walls/floors.

Well, I just moved the stuff to my girlfriends place. She has very high ceilings, hardwood floors, a big area rug. The speakers are in front of sliding glass doors. The side walls are slightly close to the speakers. Although it sounds pretty good, I am still having the same problems with the base. It is slightly muddy, with no tightness or slam. I have tried moving the speakers closer and further from the glass, but that only changes the intensity of the base sound, not its quality.

Could it be the glass doors behind? (I did have similar problems with the speakers in front of windows at my place.) The kestrals have a passive bass design, with a big hole in the lower back of the cabinet. Maybe it requires a solid wall behind it. Is it the side wall reflections? I have heard the arguments against metal cabinets, but does that effect base?--the base did sound fantastic with the same cabinet in the first set up.

I have a feeling the only answer is to turn my girlfriends apt. into a sound studio, but she isn't too keen on drapping her walls with sound baords etc.

Any suggestions?

THanks,
Steve