10k 300B single ended amp, what should I choose?

Check this guy out. http://www.experiencemusic.net

You will get much more for your money with a custom built amp from a guy like Jeffrey. The quality of parts will be higher than a commercial amp and the sound will be incredible. He can build it to suit your tastes and other equipment.

Indeed, you'll need a very hefty 300B to reproduce large orchestral works with ease especially if you want one amp to drive the spkrs full-range (I would suggest you use another amp for the bass).
DIYing is an excellent option, as suggested above. Also check out a refined classic designed at goodsoundclub.com.
IMO this investigating is well worth doing BEFORE you invest 10k in a commercial product!

I 2nd Hermans recommendation of Jeffery. AND he's a great guy too!
Good Listening!

Thanks for the suggestion. I'm thinking bi-amp using the Mastersound for the bass and some 300B for the mid and high. I never knew about jeffery but will sure give it a try.

Not that I'm trying to change your mind on getting a 300B amp . . . but have you considered a SET amp that uses the PX25 tube from Art Audio or Audion? I too was thinking 300B, did some listening and finally spoke with Joe Fratus who is the owner of Art Audio on USA as he makes/sells both the 300B and PX25 amps. In his opinion the PX25 amp was the better of the two so I bought it and have been extrememly happy with it. It is a very strong sounding 6watts/ch. but with my 97dB efficient speakers and high gain preamp I can only turn the volume up a few notches before getting too loud for the wife.

Give Joe a call - he's a great person to chat with and not pushy at all. Very customer focused. And the price of the Art Audio PX25 is US$6,500 so it's within your $10K budget with bucks to spare for music presumably . . .

Kevin