Speaker - Room/size dilemma


Need some advice. Like many other (married) folks here, I'm trying to find a reasonable balance between room esthetics and sound quality. We listen to music in our living room. It's a 16'X18' room with a two-story ceiling that is almost 20' high. So the room is basically a large cube. The other challenge is the speakers need to be placed along the18' wall, roughly a foot or two away front the side and the back walls, basically near the corners since we have a fireplace in the middle of that wall. The couch will be about 15' away from the speakers. All in all, the speakers and the main listening position form a 15' equilateral triangle. I guess I'll need  to look for high dispersion speakers with good off-axis sound quality. Almost the opposite of what I have in there now which are ML Aerius i speakers. I still have the pair of Definitive Technologies BP20 speakers which I had originally purchased for this room and I think they better fit that application but I really prefer the clarity and focus of the MLs albeit with a much more constrained sweet spot. The MLs are being driven by a McIntosh MC2200 and I have the Def. Techs in another (smaller) room hooked up to a Vincent SP-331 hybrid amplifier. My bottom line question is what would be a decent option for this cubical size room, trying to stay within a $3K budget. The bi-polar design speakers seem to meet most of the requirements but sound a bit diffused to my taste. Anyone has experience with the newer/slimmer Def. Tech. tower models? What about the Magnepan 1.7? Thanks in advance. 

128x128kalali
There's a pair of Joseph Audio Prisms for sale here now in your price range that would be worth a look.  A lot of the Pulsar's performance for half the price. 
Had been looking at various dedicated listening room plans for 12 years, and ended up with a Cardas Audio design called a "tapered trapagon".  It is roughly 20' L x 14' 11" W (dead end) x 13' 6" W (live end), with the ceiling sloping from 8' 7" to 7' 8".  The side walls are non parallel.  Added very little acoustical treatment (thick carpet, etc.), but did end up with a 4' x 8' ceiling "vent" with light batting to allow for air flow.  It was rather easy to construct in an open heated basement with a 9' 6" ceiling.  As an added note, took the opportunity to upgrade to dedicated AC lines for the audio gear.
I agree with all of the room treatment advice (and there some decorator-friendly options from GIK, ATS, and others). However, even after applying appropriate treatment, a room with those dimensions is not going to have even bass response without digital room correction. Check out Mitch Barnett's book, Accurate Sound Reproduction Using DSP.
Kalali, a note regarding the Magie 1.7: I do have and in a closely sized room, but only 11' H. sloping to 8' at the walls, Trying to accommodate WAF, I found at only 2' from the rear wall, just didn't work. Moved them out to 3' - much better and at 42.5" toed very slightly in, WOW! It only took a few days and a little listening to convince the wife that them living a ways further out wasn't so bad. I did hang some acoustic drapes on the walls behind. With a little patience and work at toeing and slight changes in placement the rewards in detail, image and stage is amazing.
Good luck with your quest,
Jim 
I've never tried a DIY solution, but the GIK Acoustic Soffit Traps are among the highest value bass traps you can buy.  They are unique in how deep they go for the space and money