I just traded in my Pass Labs INT-150 for a PrimaLuna Premium Dialogue HP (Really, couldn't they have come up with a snappier name?) and I LOVE it! It's so much richer and simply more realistic sounding compared to the Pass. It can use EL34 (which is the stock tube), KT 88/120, or KT150 tubes. What differences in sound would I likely notice among those tubes? Thank you.