Guys, I feel it would be remiss of me not to warn you about Dennis Fooley. Apart from him frequently offering dubious information he has spent time in prison. Best to steer clear.
To those who think that bass traps do not belong in corners here is a simple test. Play something with a prominent beat and then walk around your room, you'll find plenty of bass in the corners and this is where you want to place bass traps. Bass builds up in places other than the corners just not as much and you would not want a large bass trap/s sitting in the middle of your room. Corners are easier to accommodate and more effective.
Multi-subs properly set up will help tame the peaks and nulls and really improve your sound but benefit from some absorption to reduce long delay in decay.
If going to subs to improve your acoustics, which I strongly advise, choose sealed rather than ported and it's essential that they have continuously variable phase.