Cary 300SEI with KR 300BXLS tubes

Does anyone have experience comparing the stock 300SEI with the sound after changes to run the KR Audio 300BXLS tube? I understand that the change makes possible 20 watts/channel instead of the stock 11-15 watts. I have inefficient speakers (Fulton Premieres) but want to use a 300B-based integrated amp if possible. Any information would be greatly appreciated. Thanks.
I can't comment on the power gain or the sound in the Cary directly (so my reply may not be terribly helpful!), but I have done a lot of 300B comparisons now in other setups and Idid want to say that the 300BXLS tubes are truly remarkable! They are amazing top-to-bottom performers and tremendously musical without being euphonic. Any additional power you may gain (assuming you can adjust bias as they describe), will be an added bonus - I had no power gain in my VAC amps, but just enjoyed the performance.

Good luck - I hope you can make them work!

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.