which 300b tube sounds the best?

Ever since I put KR 300BXLS in my CA-339s I stopped chasing power tubes. Yeah, they're pricey, but I even preferred them to WE in my Wavelength Tritons.

Tomryan, I'm just a new 300B tube shopper like yourself. I got the Svetlana 300Bs for now. Looking for something different and better.

Are the KR 300BXLSs usable in all 300B amps or are they just for the higher output versions? I'm using W.E.s now in the Air Tight ATM300 and would like a bit more body and warmth.

They are a drop-in replacement for standard 300Bs. I've used them to good effect in two amps designed for regular 300Bs, as well as in an amp specifically designed for them. I don't know if they will give you more body and warmth, though. The differences I heard were greater linearity, better dynamics and extension as well as a cleaner overall sound. In one case I compared them to WEs and Sophia meshies, in the other to EH.

If I was looking for more body and warmth (which to me says "midrange bloom") I might look in another direction. OTOH, I's suggest you try a pair of KRs anyway, because their other characteristics are so appealing it might turn out that's what you've actually been looking for.

S23chang,
I have only compared the 98-C to the regular Valve Art 300B, it was a huge improvement smoother with more detail, and the Western Electric, pretty much even, I would say the 98-C had a bit more resolution and the WE more body and warmth. The differences between the WE and 98-C would best be described a subtle, at least to my untrained ears. Hope that helps.