New tubes...far more power??

I am not aware of anyone manufacturing KT150 tubes other than Tung Sol. As far as tubes not inproving/settling in with some burn in, is not what my ears tell me. Just sayin.

Have you unplugged the amp since removing the old tubes? Your auto-bias circuit may be retaining the settings it used with your old tubes. Sometimes unplugging the amp resets to "factory settings". Leave it unplugged for an hour or so. I'd even remove the new tubes after unplugging ( plug them back in before restart). 

I will try the unplug suggestion, will be using my back-up amp ( a ss design, which does make for a lot less nervosa) for a week or so.
Last night, I was pleased to hear that the tube amp was in fact sounding a lot better, the increase in power was still very evident ( and strange) but the overall SQ was fuller and less bright. I moved a power cord off the preamp and replaced it with another brand...this could have helped.
Here's the interesting thing, my ss amp puts out 250 watts/ch into 8 ohms...and nearly doubles into 4ohms, my tube mono blocks put out 48watts/ch into 8 ohms and not much more into 4ohms...yet the tube amps sound FAR more powerful than the ss amp. ( Yes, the tube amps have massive transformers, while the ss amp has slightly smaller transformers..and the tube amps are mono blocks, while the ss amp is a stereo amp...but the power output in volume is strikingly different...and adverse to what one would expect!) 

What is the brand and model of the tube amp?

Yes! Tubes break-in and age during the first 50 hours of use.

Davey f you must be a tube novice IMO.

@don_c55 you are right, I am a tube novice, having owned tube amps and preamps for more than thirty years.
Plenty of assumptions here. Including that these tubes need to be broken in..
as they were played for about 200 hours when I first acquired the amps (Jadis mono blocks) and were then put aside in favor of the stock KT150’s that came with the amp.