Not sure what your definition of "big monitors" encompasses. If "monitor" means "sits on a stand", and "big" means "BIG", then...
I hope you don't mind a dealer chiming in about something he owns and sells, but you might consider the GedLee Summas. They disappear as the apparent sound source - no distracting resonances, diffraction, colorations, or response peaks to tip you off. The bass doesn't extend down extremely deep (probably ballpark 35 Hz in-room), so your plan to add subwoofers would work well. Your 40-watt amp would never break a sweat driving them.
As of this posting, the price on the Summa is in the five grand ballpark. I know you're prepared to spend more, but if you can live with the Summa's size and unorthodox, form-follows-function cosmetics, I don't think you'll find their sonic equivalent below ten grand.
As far as state-of-the-art goes, the Summas were designed by Dr. Earl Geddes, the world's foremost authority on waveguide design and a consultant to numerous leading manufacturers. The Summas use a very high quality 15" prosound woofer crossed over at about 950 Hz to a very high quality compression driver mounted on a 90 degree constant-directivity oblate spheroid waveguide. The crossover point was chosen to match the radiation pattern of the woofer with that of the waveguide. The waveguide features a patent-pending refractive index (or foam plug) which eliminates a type of distortion common to horns known as "higher order modes". Briefly, sound that bounces side-to-side down the mouth of a horn is undesirable, and the foam selectively attenuates those sound waves more than the "good" sound that makes only one straight pass through the foam. The crossover corrects the frequency response taking into account the presence of the foam. I think it's safe to say that the GedLee Summa is at the forefront of advanced acoustic design.
Dr. Earl Geddes and Dr. Lidia Lee, the principals of GedLee, have conducted extensive ground-breaking research into psychoacoustics and audibility of distortion. The commonly-used yardsticks of distortion measurement do not correlate very well at all with our perceptions, and therefore are not very useful. Our distortion perception has tolerances and intolerances (thresholds) that are decidedly non-intuitive. In the design of the Summas, Dr. Geddes has focused on minimizing those distortions that are most audibly significant - many of which other designs make little or no attempt to minimize. Even DSP (digital signal processing) cannot solve those problems that require an acoustic solution, such as diffraction and the above-mentioned higher order modes.
I have had several people comment that the GedLees don't sound like speakers, that you can't hear the crossover, that they don't sound like horns, that their depth of image is outstanding, and so forth. Once in a blind test, one of the partcipants thought we were listening to electrostats. I also sell full-range electrostats that this person was quite familiar with, so that's a pretty high compliment for a "horn speaker". Ahem, "waveguide".
Feel free to hit me with any questions you may have about the design of the Summas, or you can check out GedLee's website at http://www.gedlee.com/
Best regards,
Duke LeJeune
AudioKinesis