You seem to have what would be a beautiful room. No dimensions that are multiples of each other and a GOOD size so you can experiment with near and far field listening. My advice : First, start at the source. I've found that even modest speakers can sound GREAT when driven by first class source components and amps (not to mention the cables). An old auditioning tool I use is a good set of headphones that has the tonal balance and detail resolution that suits me. Then I can audition my source components without the room getting in the way. Very effective and VERY revealing of the source. Second, or maybe in conjunction with first, see if you can get a real time analyizer (with 1/3 octave resolution)and do some measurements around the listening seat. Who knows, you may have a small spike or roughness in the two octaves from 1-4 KHZ or in the 10-12 KHZ (FOCALs problem area) region both of which the ear is extremely sensitive to and can enhance detail. Most cone speakers have their tweeters below ear level but are designed to be smooth on the tweeter axis. This can lead to severe lobing vertically. Try tilting the speakers back. Also, a dip in response in the lower midrange and/or upper bass can also have a similar effect of enhancing detail even though the upper octaves are smooth. I find that I prefer a slight counter clockwise tilt to the tonal balance with the upper octaves down about 3-4 DB relative to the upper bass. A flat response at the listening seat (assumming a dome driver)can sound just too cool an analytical no matter what the source. If you find that you are still just to sensitive to metal domes and can't afford the price tag associated with the better soft domes, you may want to try a WELL designed ribbon or ribbon hybrid from Nueform or, if you can find'em an Apogee Slant 8, Caliper Signature, Duetta Signature, Stage/Mini-Grand, Studio Grand or Diva. All of the Apogees, except the Divas & Studio Grands, can be had for under $2000. They all have a "robust" tonal balance, tons of unforced detail, and are exceptionally quick when properly fed (lots of class A biased, solid state current). Your room would be well suited for them. Good luck! P.S. How loud do you listen? That peak in the response above 25KHZ for metal dome drivers CAN be detected with some people who have very good hearing and listen loud enough to bring that response burp up above the noise for their hearing.
