$1,000 to spend on room treatment....

My new room 21*13*7 has very bad acoustic: flutter echo of hell (a solid 2 seconds of metallic echo for each clapping of hands), bass resonance and probably more that hides being the first 2 but that will become noticeable later on. I have a max of $1,000 to spend to treat it and already own 4 fiberglass panels 2*4 that I can use to treat mids and diffuse. What do you suggest - price when new to be consistent? There are some room kits that seem to fit the bill (www.primacoustic.com) but I need guidance on this. Tks.