Another vote for 845Bs. I use them in a pair of Cary 805Cs. I've only compared them to the other Chinese 845s (845A and 845C). To me, they are richer, fuller, and more musical than the standard Chinese 845s. Depending on the rest of your system, you might prefer the 845Cs. These are more detailed with deeper, tighter bass, but are also much brighter sounding. If the rest of your system is dark and warm sounding, these might be the way to go.
By the way, you don't state what 300B tubes you are using, but if they aren't Western Electric, I'd make that upgrade first before upgrading the 845s.
By the way, you don't state what 300B tubes you are using, but if they aren't Western Electric, I'd make that upgrade first before upgrading the 845s.