Hmmm - I am not sure what they sold for new. I bought this one from our own JohnnyThunders. I have never swapped the tubes, but according to the manual there is rebiasing involved. The bias control pot is available without opening up the amp, though. It supports a whole handful of different power tubes. Manual is here: http://www.groovetubes.com/pdfs/S45_Manual.pdf This amp and the GT-8 are the closest I have found to getting a pretty realistic bunch of usable tones from a modeler. The amp seems to give the digital effects a life they were missing. On its own, it is a very clean amp, even at high volumes. There are lots of controls to change the overall sound, but for the most part it just provides an assortment of cleans. The reverb is not so great, but it's not terrible either. There are a few threads on the Gear Page where people discuss their settings and impressions. I really like it quite a bit, but it's not in the cards at the moment.