Need help with room

I currently obtained a SPL meter and Rives test CD to try and diagnose why my system is fatiguing in the highs and lacks in the mid bass. When I performed the frequency analysis I noticed that I have a rather steep decline in decibels below 400 hz bottoming out at 125 hz and then rising a little to 100 hz then back down. On the other end I have a sharp decline above 6300 hz. The total swing in db from top to bottom is as much as 30 db btw. 50hz and 16k hz. I would like to smooth out the frequency response and have tried moving the speakers, but it mainly just moved the lowest point a few hz without really affecting the response more than a few db and I need a lot more. I also tried different interconnects with minimal success. I tried removing my home made acoustic panels that did change things, but not to the effect needed and panels will not compensate for my base suck out if that is what I have. I am curious about my source because it does seem to lack in the lower end when compared to other sources, but I would be supposed if they could be that different. If anyone has any ideas I would greatly appreciate it.
Thanks, David

Room is 10' x 11' with 8' ceilings. Speakers are set out on golden ratio from front and sidewalls. One large window with metal blinds and thin curtain on front wall.
Parasound A23/P3
Denon 3800 (source)
Audioquest cheetah and jaguar interconnects
Alpha core Python MI2 speaker cables