Acoustic treatments are put in place for a reason
Technically, you want the first reflections to be -20db below the direct sound in the first 20-30ms or so, hence people use the ETC chart to verify that.
Doing that can be accomplished by:
-speaker selection and placement
-room design/layout features
-acoustic panel type ; absorption, diffusion, B.A.D. panels, etc
Putting panels where the do NOT impact the above may/may not be a bad thing, it depends....but why spend $ if not needed?
If applying absorbers, then putting them where not needed will absorb some sound energy, possible making your room too "dead" sounding
Ray trace simulation of my room, showing where first reflections are:
My room layout sketch, see my side wall panels and my ceiling cloud panels:
If you have 2 rows of seats, then possible you do need some treatments for the 2nd row.
Can you post a plan view to scale layout of your room?
Hard in a picture to grasp details.
Are you going willing to spend $80 for a USB measurement mic and really know your acoustics?http://www.avsforum.com/t/1449924/simplified-rew-setup-and-use-usb-mic-hdmi-connection-including-measurement-techniques-and-how-to-interpret-graphs