Alas, I have an alternate idea...Try getting some new, higher quality tubes (I'm assuming the stock tubes are in the amp - if not then disregard everything I'm about to say lol). Then, get the amp biased properly. You'd be amazed in the difference that good tubes and a proper bias can make in your amp's overall tone. Then, use a nice OD pedal like a Tubescreamer or BBE Green Screamer to push your drive channel into serious high-gain territory. If you're not quite familiar with different types of tubes and biasing, visit the Eurotubes website for some good information, and the guy (his name escapes my mind right now) has full retube kits for many amps including the Valveking.