There is a PWS MK109 piston upper on the EE. I have the same one and I love it, I am getting very very close to 1 moa with my 110gr handloads.
Suputin is also selling 300BLK barrels on the EE, he has 5 chambered blanks and will cut to any length and contour you want.
As mentioned SFRC has NEA 12.5 inch barrels for $210. Add in a $150 upper, a $185 12 inch forend, $50 muzzle device and if you want a $130 BCG and your ready to go.
Questar probably has complete uppers.
P&D in Edmonton had a nice AAC upper there a while ago.