Well, if you go back you'll recall that I did post that the SR-009 and KGBH are better in several areas, but switching from that $8000 combo to a $4000 HE-6/ZDT combo doesn't make the HE-6 sound bad, just not as good (my ZDT has $ upgrades). While doubling the price doesn't give 2x better sound, it does give me better sound than any other headphone rig that I've tried/owned.
On the other hand, for half as much money I'd be perfectly satisfied with the HE-6 rig if I couldn't afford better. The contrast of switching from 009 to the HE-6 (or O2 Mk1/HE-60/HD800) after acclimating to the 009 isn't as dramatic as switching from SR-009 to something like HE-500, LCD-2 r1 or HD600. Switching down to the HF-2 is an even bigger "Yikes!"
Well, if your talking about bang for your buck, my 009/727 combo cost me about 6K new. What about your WES, I would think that the WES and SR-009's cost you over 10K "Yikes!!!". Anyway for about 2K you can upgrade to what many think are among the best headphones and a great amp that are being made now, from a ZDT (with stock tubes) that some say is under powered for the HE6's. Matter of fact add in the cost of your tube upgrades for your ZDT and the gap starts to narrow, becoming less and less.
Also you seem to suggest that the WA6 can properly power the HE6's, my experience with my max WA6SE was that in no way could it properly power my HE6's.