@Jeb's and others' tube reviews were super helpful, but thought I could add some updates since prices for some of those tubes have gotten nuts. I have found myself with A BUNCH of tubes. I bought a Crack with Speedball that came with some tubes, including Telefunken ECC82, for what I thought was a decent price, then managed to pick up another Crack with Speedball for about the same price that came with Mullard CV4003, Tungsol 5998, and a goldpoint stepped attenuator [so can sell the first one whenever I have time to replace a diode that came loose ]. Before the I got the second one I had picked up what I hoped was a lightly used Chatham 5998. Also a pair of Svetlana, and a few of the cheaper options that are recommended around the web. Power Tubes: Tungsol/Chatham 5998: is damn expensive. $125-175 ---It's a set it and forget it tube. I've had not desire to switch to one of the others. ---Maybe worth the high price to not have to worry. The space and air is impressive. Adds a subtle playfulness to the music. Very low noise floor. Svetlana: Cheap ---There is a bit of harshness. If that were gone would be very close to Tungsol 5998. ---If you've got a mellow signal could work well. ---Has the air and separation that makes the 5998 special. Low noise floor. RCA 6as7g: Medium price ---Sound very nice. Mine has high noise floor and some microphonics issue otherwise would be great. I could totally live with this over the 5998 if the noise/microphonics were lower. RCA JAN 6080: low/med price ---Like RCA 6as7g, mellow but satisfying tone, but again mine has high noise floor. Not the 'best', but totally fine other than noise floor. Cheap Option: Svetlana is a little harsh, so find a good copy of RCA 6as7g or even RCA JAN 6080 and I think you'll be sitting pretty good. Signal Tubes: Here's where the fun is...and the fun is cheap. I should preface that a lot of the tubes don't have enough bite for classical music for me. I like to hear the sharp edge of trumpet and violin. I'm pretty sensitive to sibilance, but still like my violin to capture the abrasiveness when appropriate bordering on caustic. Expensive ones... Mullard CV4003: The Good: Little Black Dress tube. Perfect for all occasions. Non-fatiguing. The Bad: Expensive. Too mellow for some music. Missing bite. Telefunken ECC82 Ribbed Plate: The Good: Fun level of extreme detail that is nice for classical music. Non-fatiguing even with level of detail. The Bad: Expensive. Weird echo that is super annoying for anything like blues that already had a lot of echo/reverb in it. The Cheap ones.... Amperex ECC82: The Good: Low/Med priced. Non-fatiguing. Could match well with harsher drive tube. Bit more lively than Mullard. 'Pleasant'. The Bad: Too mellow at times. Too middle of the road (like Mullard). Siemens ECC82: The Good: Med priced. Middle Ground. More detail than Amperex. The Bad: Less articulare bass than CBS 5814A.GE USAF 6189: The Good: CHEAP. Just a fun fun fun tube. I can't listen to classical without this tube. Has most of the detail of the Telefunken without the echo and with more mid and low end. The Bad: A little fatiguing for rock or harsher music.CBS 5814A: The Good: CHEAP. Really nice everyday tube. More lively than Mullard, but less detailed/echo than Telefunken. The Bad: Not much. I like more bite and sharp edges for classical. My daily drivers have become a tag team of GE USAF 6189 and CBS 5814A. 5814A is general purpose and the 6189 is if I know it'll be a longer classical music session. Sometimes I'll be listening to classical and feel like something is off and realize the 5814A is in. Super cheap. I like them so much I bought a spare of each. Probably <$20 for 2 of each.