Tbromgard - I hope you enjoy your Jolida 502 as much as I did mine. The tube complement recommended by the Tube Store sounded great. Unfortunately, the JJ KT88s just did not seem that reliable. I had a couple fail in well under 1000 hrs and on at least one occasion necessitate an amp repair. Ultimately, I went to Winged C SED KT88s purchased from Upscale Audio. That isn't anything against the Tube Store. I have subsequently purchased and will purchase again from them. The Mullard and Ei Elite small tubes they sold me were just fine. Because I changed all the tubes out at the same time, however, I can't give you any impressions about their individual contributions to the overall sound. Before you do any tube rolling, do take some time to get familiar with how the amp sounds in stock form. I think the Jolida represents good value and it does benefit from some relatively inexpensive tweaking. I heard improvement from the following: Herbie's Tenderfeet between amp and hardwood cutting board used as platform for it; HiFi Tuning Fuse; upgraded power cord. I went with a MAC Soundpipe but today would also consider a Pangea AC-9. Finally, after you have lived with the amp for a good while, get in touch with Jolida. Call them direct and find out about their factory upgrade. It was maybe $250 or a little less when I did it. Thought it was well worth the $. Noted greater clarity and a bit more detail as well as deeper tighter bass from it. Wished I had done it sooner. I don't use the Jolida day to day anymore but did keep it as a backup. While they sounded great with the Jolida, the Totem Forests I was running really needed more power so I eventually got some higher power tubed monoblocks. If WAF allowed, I would love to get a 2nd set of more efficient speakers (e.g., Tekton Lore's?) to use with the Jolida from time to time. Good luck with your 502B. Again, I hope it gives you many hours of listening enjoyment.