I have Cary 300B SE monoblocks which I have used KR 300BXLS for comparason.
If you have normal Cary 300B SEI version, just putting KR300BXLS will not give you 20wpc. In order to get full power potential of KR300BXLS, you need to have the amplifier built specifically for KR300BXLS optimum parameter(higher bias, sturdier transformer which can handle higher current/voltage of KR300BXLS, etc.)
At normal 300B bias setting, KR300BXLS's still have more authority and better bass control than other 300B tubes in my Cary 300B monoblocks. Overall, it sounds little darker than other 300B tubes I have used. If you are looking for better bass and don't mind loosing some of the WE300B midrange magic(I say some, KR300BXLS still has 300B midrange magic), KR300BXLS are good tubes to try.
If you have normal Cary 300B SEI version, just putting KR300BXLS will not give you 20wpc. In order to get full power potential of KR300BXLS, you need to have the amplifier built specifically for KR300BXLS optimum parameter(higher bias, sturdier transformer which can handle higher current/voltage of KR300BXLS, etc.)
At normal 300B bias setting, KR300BXLS's still have more authority and better bass control than other 300B tubes in my Cary 300B monoblocks. Overall, it sounds little darker than other 300B tubes I have used. If you are looking for better bass and don't mind loosing some of the WE300B midrange magic(I say some, KR300BXLS still has 300B midrange magic), KR300BXLS are good tubes to try.