I actually have spent a bit of time listening to Meadowlark Kestrel HotRods being driven by a 300B Cary 300SEI integrated SET amp about 5 years ago. The sound was very warm, smooth, and engaging. A bit soft on the top and bottom ends, but I later realized that had more to do with the Cary than the HR's when I had a 300SEI at my house for a few weeks.
So, I don't doubt that you can get great performance from Meadowlarks and 300B's.
It's not clear whether you are hoping to find a 300B PP amp putting out 20-40 watts per channel or 20-40 watts total(10-20 per channel). 20-40wpc is nearly impossible with a standard 300B being kept within it's most linear range of operation. Most amp designers like to keep the 300B somewhere between 6-8wpc single-ended, 10 wpc is really pushing that tube to it's max cleanly. PP results are simply twice that amount. So, a really good PP amp that is staying in the sweet spot distortion-wise, will most likely yield 12-20 wpc at most. I know Cary and some other manufaturers like to claim 15-20 wpc single-ended, but that kind out output is highly suspect. It's possible, but you probably won't find them quoting distortion specs anywhere near their max.
Manley Laboratories makes the
Neo-Classic SE/PP 300B amp that puts out 11wpp SET and 24 wpc PP. Their amps are extremely well made and sound fantastic. Not cheap, though.
The other options are amps running the monster 300B variants like KR Audio's 300BXLS tube. These puppys need a lot more current to run, but will legitimately put out 15-25 wpc SET. Although, if you simply drop these tubes into a standard 300B amp without current modification, you'll only get the normal 8 wpc.
Art Audio and KR Audio, itself, make 15-25 wpc SET's using the 300BXLS tube. They're awesome, but pretty expensive. I don't think I know of anyone making PP amps with them.
Don't write off 845 SET amps, they kick ass and I like them just as much as 300B's. You get 16-25 wpc of meaty, luscious, power with serious low frequency punch.
I think it will easier to find a great 845 SET than it will be to find a great 300B PP amp. Price-wise, neither will be cheap.