1st, visit the GIK circle here at Audio Circle and give them a call.
2nd, lose the foam which as best is a narrow (frequency) band absorber.
3rd, lower the ceiling to 8ft (assuming one of your 10ft dimensions is room height).
4th, pull speakers/listening chair away from all walls (speakers at unequal distances from front/side walls).
5th, replace foam with high density Owens Corning 703 fiberglass (one of the best wide band absorbers) at first reflection points.
6th, if you still want diffusion make sure it's depth is random (quadratic), made from dense material (not absorbent), try to go for blocks (not strips that only work in one plane), locate at first reflection points, and realize that diffusion requires depth to work so the most effective are 7.5 inches deep but only cover down to roughly 1,100 Hz. Go to
http://www.pmerecords.com/Diffusor.cfm for the best recipe I've found. Note that each 18 inch x 18 inch x 8 inch panel will weigh 23 pounds but are cheap/easy to DIY.