Acoustic Damping Behind Speakers?


My speakers are placed about 3.5 feet from the wall behind them, which is just drywall. I get a funny echo from the wall and have been using the cushions from the sofa as dampers, which actually work fairly well. I can't imagine why, but my wife does not think this is an ideal solution, so I'm looking into some sound deadening options.

I was looking at Acoustimac panels, which are reasonable at about $50 each. Does anyone have any other favorite - and reasonably priced - products?

Also, at this point I'm only contemplating using two, placed directly behind the speakers. It would be difficult to get any more past 'she who must be obeyed'. Would this be sufficient? The room has a lot of stuffed furniture in it.

Thanks!
grimace
I purchased panels from this company when Sal was a member of AudioGon a few years back.

The panels are very nice and can be mounted vertical or horizontal and have a zipper so that the cover can be removed and washed if needed.
I've used ASC sound panels for years. I have 4 and they are highly effective.

I think they come in boxes of 8 which maybe more than you want...

http://www.positive-feedback.com/Issue22/asc_soundpanels.htm
I like ATS Acoustic panels. They are relatively inexpensive and come in a variety of fabrics. They also sell on ebay which is where I made my first purchase with them.