While I think that may be just seen as contrarian, I have noticed an effect just by switching to only ethically sourced meats. The quality of grass grazed, un-processed beef and chicken is almost unlike what you see in the supermarkets creepy saran wrapped isles.

Yes. Not just quality, but taste is also positively affected.

The ground beef I get from http://www.lamauve.com/ for example tastes so much better than that of local grocery stores (which always has a slightly bitter and uninspiring taste).

I'm carnivore too. I was going to make the point to the OP that the mental clarity, feeling of wellbeing etc. is probably due to abstinence from processed carbs i.e. sugar, not plants