i agree that long wall speaker positioning is the way to go (as it greatly ameliorates side wall reflections), but it does create its own problems:
1) bass articulation
2) staging
3) top end extension
IME you cannot overload the room w/ bass traps---put them in the corners to start (lots of DIY solutions for very little money--search Jon Risch). but you've also got to reduce standing waves between the walls that are 12' apart (check for slap echo; if its present, add wall panels--OC 703 is a nice product, put that covered w/ some polyester battling over top on the wall behind your head and see if you notice anything. its a $50 experiment).
1) bass articulation
2) staging
3) top end extension
IME you cannot overload the room w/ bass traps---put them in the corners to start (lots of DIY solutions for very little money--search Jon Risch). but you've also got to reduce standing waves between the walls that are 12' apart (check for slap echo; if its present, add wall panels--OC 703 is a nice product, put that covered w/ some polyester battling over top on the wall behind your head and see if you notice anything. its a $50 experiment).