Going 3:1 on an image shot on my 5D3 looks plenty good to me. Mind you, I don't print 10 foot tall images to hand about with a magnifying glass to my friends either.
Yes the Nikon 800 series are great, well their sensor is anyway. Yes I have shot with one, but there is a lot more to look at than just the body. Don't worry though as Canon or Sony or Fuji or... will come out with something better soon. Me? Well I find Nikon clunky to use as I don't use the D800 enough to get use to it.
Go try a medium format camera if you want better image quality, slightly bigger difference between one of those and the DSLR's tit for tat that goes on in the marketing world of selling you crap you don't need.