I agree with Gammajo. The stock tubes in the preamp are very good and provide wonderful musicality. The upgraded tubes do make an improvement, but depending on the resolution of the rest of your system, the difference isn't huge. For me, the early 60's Siemens grey plate CCa tubes just fine-tuned the overall sound to give me the ultimate tone and timber of instruments. The preamp is so transparent that cable and power cord additions can clearly be heard. I recommend that you start out with the stock tubes, or Joseph's upgraded Siemens, then live with and enjoy the sound for a while. Experiment with tweaking the cables, power cords, and room acoustics until you've extracted the best sound possible. Then find a hopefully good deal on the early Siemens CCa( preferably in tube locations 1 and 3) and you'll hear the magic of Joseph's preamp more clearly. Enjoy the journey and happy listening.