I have found GIK as recommended above, to be a good reasonably priced source for acoustic panels. I installed them in our previous house and plan on using them in our new one.
If the application allows, I prefer the aspect of free-standing/movable panels not only for initial trial placement purposes, but also for present and future flexibility. In fact, GIK just sent a flyer out last week mentioning their new "Panel Foot Kit" that will turn almost any of their products into floor standing/movable ones: http://https//www.gikacoustics.com/product/panel-foot-kit/
If the application allows, I prefer the aspect of free-standing/movable panels not only for initial trial placement purposes, but also for present and future flexibility. In fact, GIK just sent a flyer out last week mentioning their new "Panel Foot Kit" that will turn almost any of their products into floor standing/movable ones: http://https//www.gikacoustics.com/product/panel-foot-kit/