looking for tube info

I'm guessing that you are now getting a fairly mellow sound lacking any sense of dynamics and crispness, i.e. an overall dullness. With new tubes you should expect a marked increase in dynamics and detail. Tighter bass and extended highs.

FWIW I use the SED KT88 in some amps but thay are not necessarily optimum in all amps or systems in that they have a bit of bloom in the upper bass and upper-mid range brightness to which some folks object. There are other models of KT88's which are a bit more linear in general. A lot of amps also accept 6550's, a much more linear tube, and this woluld give you a wider choice when replacing your present tubes if your amps can use them. It really boils down to what type of system (including the amp!) you have and what tonal quality is important to you.

Also consider the possibility that the small tubes may be used up and need to be replaced. They also have a substantial influence on the sound.

What do you mean by "effect"?

You didn't identify the amp in question but from an electrical standpoint the new KT88s should work without adversely affecting the amp.

They will probably sound a bit different but that may be as much due to old tubes versus new (tubes lose performance as they age) rather than the different versions involved.

The best you can really do is try different tubes and see if you prefer one brand over another. That's called "tube rolling." Different people may reach different conclusions.

I'm confused about your amps. You have mono amps with 4 KT88s in each amp and they are rated at 70 watts? Are they triode? What are these mystery amplifiers anyway?