I didn`t try, but now there`s good (Shuguang/SuperTnT) 845 on the market - but 700-1000V is only for very experienced players. PP 300B - I agree, in all the charts for any tube, SE is something like Ra=4k and PP Raa=3k or so?! Probably - more power, distortion cancelation, NFB loop, AB class thinking.