Currently planning for 2 seats.
Just to clarify, 2 rows of seating or only 2 seats (2-person home theatre)?
Accoustics seems to be the major headache.
Acoustics shouldn't be a major headache. The first thing you can do to get smoother frequency response (fewer peaks & dips) is speaker/subwoofer placement.
If you blow across the opening of an empty Coke bottle, you can get that small chamber to resonate (make that booooooooh sound). If you enlarge that Coke bottle to the size of your 24x14 room, that large chamber will still resonate (at different frequencies, of course).
The 14 foot width of your room will cause resonances (room modes) at roughly 40Hz, 80Hz, 120Hz, 160Hz, 200Hz etc. Which means that listeners will hear loud peaks and quiet nulls at those frequencies, depending on where they are sitting. You can cancel the 40Hz mode by placing a subwoofer at the midpoint of room width. You can cancel the 40Hz mode AND the 80Hz mode by placing a pair of subs 4.5 feet away from the side walls. The next few modes can be cancelled by placing your L/R speakers 28 inches away from the side walls. The cancellation will improve the frequency response across the room (all seats, all listeners).
With major problems below 200Hz addressed using speaker/subwoofer placement, problems above that frequency can be addressed using treatments. This is helpful, because trying to treat bass problems requires treatments that can be up to several feet thick, which is impractical. Instead, more practical to use placement (doesn't cost anything to move speakers and subs around).
To absorb frequencies above 200Hz, the treatments can be thinner than bass traps. Somewhere between 6-8 inches thick would be effective. However, this is one of the very few things in acoustics where you can get something for nothing. Rather than building an 8-inch thick absorber, you can use a 4-inch absorber and place it 4 inches from the wall. The 4-inch air gap will make the 4-inch absorber almost as effective as an 8-inch absorber (but using only half the material).
I am confused as to go for DIY treatment or accoustic panels like anutone, armstrong etc.
I'm not familiar with Anutone or Armstrong, just get insulation material (fiberglass, rockwool, etc) that is around 2.5 to 3.0 pfc (pounds per cubic foot). If you can find that locally, you'll save a lot of money by going the DIY route. Build thin wooden frames that are 4 inches deep, place the material inside the frame and wrap the whole thing in a breathable cloth (speaker grill cloth or even just plain old burlap).
