Thanks everyone for your responses. My current system includes Granite Audio 860.1 (KT88 monos), Consonance 2.2 CDP and Equation 25 speakers. Although tubed, it is very fast, detailed and transparent- perhaps too much so for my tastes. The higher power 300B amps caught my eye as adding a little richness to the midrange, while still keeping much of the positive aspects of the speakers and cdp. It sounds as though a well executed push pull 300B may cost a bit more than than the models I am currently considering. Have a Modwright platinum Sony on the way for my other system (Plinius 9200, Harbeth S HL5), perhaps a similar change of source might be a better option.