I tried out a set of these I my Marshall 1959slp and loved them. I compared them against a set of kt77 Genalex gold lions and was quite surprised. They are not better than the gold lions by any stretch, just different. Also the kt77 tone is different in a few ways. All in all, these are top notch el34s that yield and beautiful, creamy overdrive and a great punchy bottom end. For what these cost, I will always keep a matched quad around. If you like that slightly compressed Marshall tone then buying a set of these is the next thing on your to do list!