Pepe,
Take those back to Guitar Center and buy yourself these:
http://www.gikacoustics.com/gik_tri_trap_bass_traps.htmlDo the research, the GIKs cost a little more but are much, much better. You can get them to match your decor, get a custom size, color, etc. I've used them and like them very much. Sure those foam corner traps were cheap. I had a pair and I don't think they work. Took them back and ordered the GIKs. They cost a little more but don't those bad ass expensive amps deserve the best room acoustics that you can provide?
Have you used test tones and an SPL meter to plot the room response? You can download the test tones for free. An SPL meter cost about $35. Enter the SPL values at the given frequencies into a spreadsheet. Plot the results. Draw a diagram of the room and send GIK the results. They will recommend some treatments. When you install the treatments, repeat the measurement process. You will be amazed on the change in room response. But you won't need the graph to tell you what you ears already will know.
Regards,