Are you getting 2x HD6870s for those 3 displays?!
Your 5% performance advantage is inaccurate. Even your own link to TechPowerup shows 180% for GTX480 vs. 112% for HD5870 at 2560x1600 (that's 60% performance difference). Please check DX11 games where HD5870 can't even beat a GTX470 despite an $80-100 higher price; so I have no idea about your "little to show for it" comment.
No, I am not getting wet about pointing fingers about Cayman being more power consuming, cuz I could care less about power consumption when it comes to $500 enthusiast videocards; and I am not a hypocrite about it either. I overclock my CPU and don't complain about the extra power for it. But I still giggle at biased arguments over power consumption by *certain people* who constantly brought up power consumption in every thread for the last 6 months. I bet when their "precious" brand will be in the lead, they'll somehow figure out a way to justify the additional power consumpion.
See I have no problems with recommending either brand - I am not biased. That's why I'll recommend the Cayman XT with no reservations even if it consumes 300W. Given the "strong stance" against power consumption by ATI faithful, I will fully expect none of the same people who complained about it for the last 6 months to purchase the Cayman XT because power consumption was soooooo important to them during the last generation despite a 20-30% performance disadvantage in DX11. Makes sense right?
I really think you should link to the tests when Fermi first appeared. That was when the first impressions were made.
http://www.techpowerup.com/reviews/NVIDIA/GeForce_GTX_480_Fermi/32.html