Help needed: Room Treatments on the cheap?

[kexodusc]

Helping my cousin set up his new home theater, a very nice 7.1 system consisting of the B&W 700 series driven by a NAD T763 receiver (if I've got the model right) with a Hsu Research VTF 3 sub!!! He won't tell me what he paid for everything.

We've got everything set up but the finishing touches...room treatments. Looking for ideas on how to tame the sound...

I've got to admit that I'm probably sitting to the outside of the bell curve when it comes to room treatments, so maybe I can kill two birds with one stone here and learn something to apply to my own room.

Here goes:
The room is 19' X 11.5'. (8 ft ceiling with that 80's spackling stuff on it). At present time he's got a (sigh) concrete floor with an area rug. This summer he plans to get carpeting or that wood laminate stuff that's popular, and he'll probably add some throw rugs later.
Mostly bare walls except for some bookshelfs and a table thing on the sides and back.

Surprisingly, the room doesn't sound all that bad right now...but we're pretty sure it could be better. He's already got a BFD to EQ his subwoofer and bass traps don't seem to be needed right now.

Attached is blueprint below...I think we're more worried absorbing or even diffusing reflections and taking care of behind the front speakers for now, it is a bit lively down there. Not sure the bookshelf and table are doing the trick.

I know some of you room acoustic guru's have come up with your own solutions. Being the parsimonious "thrift-o-philes" that we are (hey, he's family, what did you expect) we'd like to hear some inexpensive solutions before ordering a few hundred worth of acoustic panels.

Any ideas?