I've got a VHT Pitbull 30. My first EL84 amp. Its got EL84 Sovteks and JJ 12AX7's. The Cleans are great......very Voxey . But slightly on the metal side when cranked.........Will a Tube change effect the overdrive much or is this just a way EL84's are? Can I get a more Vintage sound out of my VHT with some N.O.S. tubes? I'm being Picky here becuase I think the amp sounds great........but I just don't want to spend good money on something that ain't gonna happen.........thanks!