Hey Charles
Though mine are long gone, look for a pair of Welborne 300B DRDs. As I mention in the article, I've listened to a ton of SET's and the Welbornes sat firmly at the top of the heap in regards to clarity. Almost zero coloration of the sound.
http://www.enjoythemusic.com/magazine/equipment/0206/welborne_laboratories_300b.htm
Hey!
Not really a 300B, but I've been using my Welborne Labs Apollo Monoblock based on KR Audio 300BXLS pumping out 18wpc since 1999. Right now I have KR Audio 842VHD tube in them. The down side is, I'm limited to replacement tubes from KR Audio or Emission Labs and they cost an arm

Still... I still love the sound of my Welborne Lab Apollo after all these years.
Anyway, I actually thought about getting a pair of the 300B DRD, but I didn't have money for another pair of amps back than when they first came out. Love the simplicity of the 300B DRD. I think they are based on Electra-Prints design or perhaps, they worked together on this.
Sadly, Welborne Labs no longer around, but I think you can find the schematic of his amps out there if you want to built one yourself. Maybe I'll build a pair someday.
Buddy