1st Acoustic Panels, maybe. Will this help?

There are two GiK Monster Bass traps for sale 2nd hand locally which I can pick up cheaper than the website price. http://www.gikacoustics.com/gik_monster_bass_traps.html

I run 5.1
B&W 805S + HTM4S powered by Emo XPA-3, Rythmik FV15HP, old polk S10's for rears, with an XT32 Onkyo 818. My sub sits between my FL and C. Planning on a second FV15HP within 6 months. Carpeted room, big fluffy sectional.

There's not a lot of options for acoustic placements in my modest open floor plan town home. I am thinking of hanging them on the front wall directly behind the FL and FR. Are these even the right kind of treatments for behind the mains? I know as bass traps they can be used in corner but I'm not looking to use them that way. I could only do front right corner, and lower 4 feet of rear right corner under a breakfast bar opening to the kitchen. First side wall reflection points are out of the question with this room+wife. I don't think I am putting anything on the ceiling but that is not completely out of the question.

Is this a worthy upgrade? If this is a worthy upgrade shouldn't I get a third to hang horizontally behind the center channel speaker with the other two vertically behind the front left and front right?

I am acoustical treatments challenged.

Do GiK Monster Bass traps effectively treat front wall reflections behind FL, C, and FR?

Did I say something wrong? Can't get no love here.

Do these monster bass traps block upper frequencies as well as lower frequencies? Will hanging these on the front wall behind the mains be an upgrade?