Speakers least affected by room acoustics

Whichever speaker you choose you will be compromised. Sound is just air waves bouncing around a room, and if you have a sub-optimal room, no speaker will fix that - just change the dynamics of how/where the waves move and thus what you hear. Have a look around this web site http://www.acoustics.salford.ac.uk. I built a custom audio room to their ratios - magically previously missing bass notes appeared everywhere - sorry, that doesn't help you.

If you like your speakers, I'd spend money on room treatments, or if you're digital, maybe try using a DSP to digitally correct the room, but unsure how it would go with echo issues. Upgrade the ceiling and put some nice panels like these in http://www.decortech.co.nz/wp-content/uploads/stCuths-project-bottom-sideimageV.jpg. or nice rugs on the floor.

The speakers that are absolutely the least affected by room acoystics are Bose 901's, if you can stand the sound at all. I can't.

I'm very intrigued by the Lyngdorf unit, especially by the all digital design. Only wonder if might sound too analytical or too "clean".

grannyring, how do you compare the Lyngdorf sound to something like an all tube pre/amp system? Does it sound as musical and engaging?

Large horns are the least effected by room issues if the fit they will work well. Horns have controlled radiation patterns thus less to reflect off wall floors etc.

I think it helps to distinguish between problems above and below the Schroeder frequency. Above the Schroeder frequency there is little more you can do than dampen the reflections. Below it is different story. Here you are dealing with room modes, and these require different measures: bass traps, multiple subs and dsp room equalization in any kind of mix that you can live with. Anyone interested in the room equalization and/or subwoofer route should now investigate the new DSpeaker Antimode X4 Preamp/DAC/crossover/room eq: http://www.dspeaker.com/en/products/anti-mode-x4.shtml
From what I understand the OP’s problem seems to be above the Schroeder frequency, but I may be wrong.