High powered single end 300b recommendations

These are awsome but not cheap.

NAT Audio Magma New. A True "do everything... For Sale | Audiogon

one other consideration for you if you go to a Parallel or Push Pull 300b you will be replacing 4-8 300b's tubes when they go, worth it? they run what around $250 each these days for average ones. re-tubing gets costly fast. 

I had a home built BeePree 300B preamp and NAIM NAP100 power amplifier. That combination gave me the 300B sound and SS power to drive my Focal speakers. Not too expensive and very pleasant to listen to. Such a combination was mentioned earlier by Snowstorm above to use a 300B preamp and solid state power amp to get the best of both worlds.

@rooze has it ... the Allnic A-6000 are 60W a side with 4 x 300BXLS in parallel, and sound incredible, in the top 0.1% of all amps in any category. Best I have ever heard vs. very costly others. The soft start means the power tubes will last a decade.

@glennewdick these 300BXLS tubes are more like $750 each, yet not to worry, I have my amps on 10-12 hours a day usually 7 days a week for 3 years. And with only 30% loss in tube life and 0% loss in power or tone.

Sadly for your needs @mikedc no integrated will get there.