Is there a concensus on changstar for what to do to get the best from the HD800 in terms of amp? Do I need to mod them, etc.? Thanks!

well, I don't think there is a consensus.  I did the anax 2.0 mod available in the other thread and you have 3 parts, the creatology foam ring + trapezoid, rug liner, and HD800's own dust cover.  some people choose to leave the dust cover off, or the rug liner off, or just have creatology foam.  Whatever you choose, the mod takes off varying degrees off the harshness of the HD800(depending on which part you choose to include/leave out) even with the stock cable.  The materials are cheap, it's pretty easy to do, it doesn't do anything permanent to the headphone, so I don't know why you wouldn't do some form of the mod.  The only hard part is getting the HD800 cushions off the first time.  subsequent times it's super easy.