Sage is not the only option for an accurazed M14. In fact, I would argue it is not even the best choice. The sage is heavy, it requires tools to strip the rifle and you have to undo quite a few fasteners. For a cheese-grater stock, it's odd that the buttstock isnt inline with the barrel. Rather than use a cheek riser to get up to the sights or optic, it would make much more sense to just mount the stock higher to lower muzzle flip.
It is well made though and gives you that EBR "Look Cool Factor".
Some other choices, all with their high and low points, include:
-AKM (MUCH cheeper and functionally almost identical to SAGE)
-Troy MCS (better for CQB IMHO)
-Vltor chopmod
-JAE
-M14Doc offerings
-m14.ca
The list goes on...
As for USGI parts, the boat has more or less sailed on affordable real GI parts now that they can't be exported from the US - unless Marstar or someone imports a bunch from overseas.
You can get milspec commercial parts, but not USGI unless you get lucky on the EE and are willing to pay $$$