ANY of the European 12AT7/12AX7s will yield a large improvement in sound. You may want to try the Ei brand, from the former Yugoslavia. They seem to have a nice open sound. All of these tubes(which is why many people prefer NOS) can be faulted in some way, but the difference between the Euro and Chinese tubes is pretty substantial. There is word that the new Sovtek 12AX7 tube is pretty decent, much better than their previous efforts. I have not tried it, so can only give you second hand information. For EL34 tubes, I only recommend two. The Svetlana are for you, if you value a soft, warm, sunny presentation. Not as muffled and slow as the stock tubes, but certainly not forward. The other tube is the JJ(formerly Tesla and Teslovak) E34L. This is a more open, dynamic, extended(at both frequency extremes), detailed sound. The JJ tubes are also available in red or blue glass. As the Jolida is an exposed tube amp, this may or may not appeal to you. I prefer the sound of the JJ E34L in many cases. If your system is more forward now, or features metal dome tweeters, then the Svetlanas may be better in that circumstance. Please also think about replacing the power cord on the 302B. Nothing extreme; just one of the cords that go for $100 - $200 here on Audiogon(Coincident, Synergistic Research, Silver Audio, and Delta are the ones I have experience with, and are all a nice upgrade for the Jolida). Good Luck