Yeh, you can tune to taste higher up the FR spectrum , however the Dspeaker does not and should not do room correction above 500hz , in fact you should limit it to well below the schroeder freq (the freq at which your room stops being a resonator) and treat all freqs above that pysically , its really not possible to correct the room higher up..albeit Dirac claims to do it.
I have been messing with DSP from way back..from the sigtech days. Still havent found a great full freq correction..
Higher freq correction with DSP is possible , but it corrects the speakers and not really the room , ie imbalances , freq anomalies etc , but it cant do anything about reflections and flutter echo and suchlike.
Clive , prior to my G1/Devialet setup , I had a set of meridian DSP6000's and twin SVS subs , Just plonked down the subs and adjusted volume an then used the Dspeaker the whole scrambled bangshoot and got stunning results..
I also had plans to biamp the Meridian heads , something similar to what you describe.. couldnt be arsed tho , it requires a huge amount of work and measuring etc..