My .02. Buy something with a pedigree if you think you might ever sell it. I built a Mega a few years back (pic is of the 260 upper). Full JP, Giessele, Bartlein with +2 gas by Craddock, SLR gas block, etc. It's been functionally 100% but I'm in it for over 3k and it's still not a KAC, LMT or...