Doki Doki Mario is pretty good. It has parts where it strays from the original, but for the most part it seems to be a bit too reliant on it. Also, unless there's something drastically different in the background, I'd stay away from using the NES-sound. The reason I'd want to hear a remix is to hear the song as if it weren't on the NES
Still, overall it's decent. I see potential in you, young Willrocker.