Great report. Thank you. I was already leaning toward the Nag. My only experience with AT is my current cart. For the price it's very good, but I find some of the highs a bit piercing and it seems to be missing something in the mids, but I like its soundstage and separation of instruments. There's also a lot of headroom when it comes to solos. I didn't know if those characteristics are throughout the AT lineup.
I don't have any experience with Nag, but I like what files I've heard that were recorded with the 300.