Since some days I am using the Sonarworks plugin for speaker calibration to the existing room modes. First you measure the room with the Sonarworks software and microphone. Then it is calculating an EQ curve suited to correct your room modes.In my case the curve looks like this:
it shows a 5dB boost at 80Hz and a frightening 9dB boost at 160Hz 
The whole lowend is massively boosted by this untreated room, making it impossible to perform any good mix decisions in these frequencies.
After using the plugin EQ correction in Logic X, the room sounds totally different, much better. A really amazing result. I do not even want to listen to itunes or soundcloud without that plugin, so I got their new product called “Systemwide”. This enables the EQ curve globally in the Mac.
I can also recommend the headphone calibration. To my big surprise, my expensive AKG-812 showed this poor curve (they deliver individual curves for all important headphones):
which is not linear at all, but quite a mess in the Mid and Hi ranges ! This means the headphone needs correction too. I verified this result with the Sennheiser HD-25. After using the recommended correction curves for both headphones, they sounded the same. So there is the question to AKG why this High-End headphone has such a poor curve !
All in all, these products by Sonarworks are definitely worth their money, especially in poorly treated rooms. Highly recommended! Will not produce without them anymore.