Is there a 300B type amp out there with some WATTS behind it?

If you have three way speakers that can be biamped you can use a 300B SET on the midrange and tweeters and a SS amp on the bass.Then you get the best of both worlds.Supratek make preamps [duals] that even have two different tubes-one for driving bass and the other mid and tweeters so you can further optimize that configuration.

Late to the party, but there is a unique and rare Cary Audio 300b amp that outputs 20wpc using KR300b XLS. 300b SEI LX-20. It has higher fixed bias, more powerful output transformers and circuit that puts 550V on the grid. Downside is the KR tubes are $1,300/pr.  I also have a Willsenton R800i 845, with 300b driving 845 output tube to 23 wpc.  
 

I can’t get either amp to one-half on the volume pot with 99dB sensitive Klipsch Fortes.  They also drive my Focal Aria quite well at 91 dB. The Cary has a taller, deeper soundstage, but not by much.  The mids and treble are about the same, the Willsenton has a touch more bass, but both have SET sweetness.  The Cary is a zero feedback design, the Willsenton is a feedback design, but the Cary distorts less at higher volume du to stability of the KR tubes.

If I had to pick one, I’d pick the Cary. I’m fortunate enough to keep both, each in a different room with different rigs.

actually there are several 300b and set amplifiers with real power

VAC RENISSANCE series 30/30 watts ren30wattsdiscontinued

VAC RENISSANCE series ren 70/70 watts ren30wattsdiscontinued

VAC RENISSANCE series 140 watts 140watts discontinued

Mastersound 845 monos 55 watts per channel in production

Dave and Troy

Audio Intellect NJ

Mastersound dealer