Proac D18 - Incurable Brightness?

Hi 

I seek some advice here on whether the slightly overly bright presentation I am getting from my Proac D18s can be tamed.  I've had them about a year and done various experiments, I do find they are much more directional than speakers I have owned in the past, but a vast amount of position tweaking has failed to remove the one trait that I don't like, and that is the high frequency domination.  On the one hand the crisp and more expressive high frequency response is a breath of fresh air after living with Mission 752Fs for many many years, and there are many other sonic advances over the Missions; they are an enjoyable speaker.  However, I do find that while the high frequencies are not harsh, and are much better controlled than I'd been used to, they do seem to dominate the scene a bit.  Mostly it annoys me with vocals, they just don't sound full enough, and I suppose in general I would prefer a weightier mid to lower mid range performance, and less dominance in the high frequencies.  

So.......one thing I am wondering is whether speaker cable could cure this.  I know we shouldn't use them as tone controls, but a sensible route maybe to dump the QED Qudos cable I've used for about 20 years, in favor of Naim's recommended NAC A5.  Does anyone else out there have both D18s and NAC A5, and if so how do you find the combination?  I would be interested to hear of experiences if anyone has moved from QED Qudos (or something very similar perhaps) to NAC A5 and how you would describe the impact?   Or let me know any other thoughts on the matter.  It maybe that ultimately the Proacs are not best suited to my tastes I suppose.  For the record they're used with DAC-V1 - Supernait 2.

Thanks