While I have not heard the modified Quicksilver amps, the EL34 tube is used in many amps and there is a lot of info available on this tube if you search around. Try the tube forum over at audioasylum.com. I have owned the Quicksilver 8417 amps as well as the Silver 90's. Great amps. I think the modification does lower the power output, which may affect the sound, depending on your speakers. I would think long and hard before giving up the Quicksilvers for a SS amp, though (unless you have a speaker like the Spendor). I tried this-tried several highly regarded amps-Classe, Audio Refinement, NAD. None of them were satisfying. Didn't want to spend a lot of money so I bought an AMC tube amp. Even with the lowly AMC, I have not heard any SS amp that has this kind of midrange, except maybe a Rowland at about $5K. However, if I had known that Quicksilver was going to modify the 8417 amps, I would never have sold mine.