Kevin,
Since your preamplifier is used you really don't know how many hours are on the tube set. AI preamplifiers are notoriously hard on tubes and sensitive to tubes that do not have a low noise floor. I would second @stereo5's advice and contact Upscale Audio regarding what replacement tubes would be recommended. For what it's worth, owner of several AI preamplifiers over the years and many tubes purchased from both Upscale Audio and The Tube Store...