Amplifier Power tubes - important to sound?

Recently bought a matched quad of 1st generation Genalex KT88 to replace some Winged C 6550 that I thought were terrific; paid what I felt was stupid money for the Genalex (of England) but had to give them a shot given their description. The Genalex are from 1955 and came in crumbling boxes. I mean these things are OLD, lol but I have to say, two weeks into them now and I've realized the hype is real. Just a thicker, more robust sound in every way. Hard to use superlatives that havent been beaten to death but they are muscular and broody tubes that really changed the complexion of my system and I'm totally smitten by the way they play. Like realizing a new set of speakers or cartridge for the 1st time; they are impactful. I'll agree the prices on some on these old tubes is getting out of hand however in my instance, was worth the spend but, I do still believe that swapping out small signal tubes yeilds the highest level of change, in my linestge & DAC anyway. If you've got the means, and many on this site do, find a reputable tube guy, listen to what he has to offer and take the plunge. These old tubes wont be around forever and non of us are getting any younger. Just my experience 

Do power tubes affect the full freq spectrum or is it more focused on below 250 hz?

Do power tubes affect the full freq spectrum or is it more focused on below 250 hz?

Of course it is a full spectrum impact. Who is claiming otherwise, and how? If I cared most about below 250Hz, I’d run solid state.

@mulveling 

Maybe I should’ve said do they impact the lower frequencies more? You own interesting speakers

Maybe I should’ve said do they impact the lower frequencies more? You own interesting speakers

@emergingsoul

Ok, I see. If you are jumping between types like from KT88 to KT90 / 120 / 150 then YES, it will usually have more notable impact on bass response - but still contributes a LOT in midrange and HF too. If you are just swapping sub-brands of New Sensor tubes of the same type (e.g. KT88: Gold Lion, Mullard, EH) then the changes are a bit more subtle overall, and not disproportionately noticeable in bass. Swapping NOS versus new production (of the same type) is probably between the 2 - I don’t have experience doing this with KT88, but some with EL34.