I finished building a Bassman clone with PPIMV mod last month, and did all my startup procedures with JJ tubes. I have a 5751 in V1, 12ax7's in V2 & V3, 6L6's in V4 & V5, and a GZ34 rectifier. I tried both 12ay7 and 12ax7 tubes in V1, but found that I like a 5751 best. I like the tone from the amp, but feel like I could get smoother gain and better harmonics from different tubes, specifically NOS that everyone insists are better. I do use the amp as a practice amp sometimes, so with the master turned down I am looking for good preamp distortion as well. If you had say $150 budgeted for new tubes, what would you get? I have been looking at KCA NOS and Hi Test Tubes, and I certainly wouldn't be able to get all new tubes for $150, but it would buy me a couple. My first instinct would be to replace V1 and V3 since I've heard that V1 and the PI make the biggest difference. Are there any particular tubes that really standout as a best buy for the money? Also, would it be worth it to think about Tung Sol 5881's in the future? My amp has around 450-460 volts at the plates. I play mostly classic rock and blues.