Not impressed so far...

[iamwappie]

That indeed is an acoustic challenge and may certainly be of influence. Just for testing sake; if your couch has separate back pillows, stack them in the corner behind the phantoms and listen to the difference. You may be amazed. Any speaker will suffer from this as it is the room acoustics but the effect may vary somewhat as it also depends on how the speaker radiates. If you really can't place them somewhere else a bass trap/tube may be the only solution. It's just not that attractive as currently your phantoms perfectly fit and blend in to the environment.