If you feel like your tone doesn't change much as you use the dials, you are probably using too much gain. There is nothing better at killing subtle tonal differences than heaps of gain. When I said that Metallica probably use huge amps, I would advise agianst you doing the same uneless you do serious gigging. Your'e never going to get a good overdriven tone with a big amp, because it will be just too damn loud. Check out the discussions that Lordathestrings has had about small tube amps in his tech talk forum.