Over the years, I have owned several "high end" tube-based amplifiers. With one exception, they have all been designed or optimized to run KT88's. Subsequently, I have spent a ton of money "rolling power tubes" as well as signal tubes. Currently, my tastes have taken me in a TOTALLY differently direction. Being a former classical musician, I strive to achieve the most realistic and musical reproduction from my system.
To be quite frank with you, the KT88 tube has never quite satisfied my tastes, regardless of the amplifier in which they were used. I have tried almost every brand, including some very expensive NOS tubes. I have also tried CRYO treatment on several. All the results have been less than satisfying to me.
Now, you mention SOPHIA ELECTRIC. That is one company that I have not tried, though I have read several professional reviews and reports, which highly praise the SOPHIA ELECTRIC products. Especially, the EL34 and the KT88 as preforming at a much superior and musical level as anything else out there.
Eight SOPHIA matched tubes is a pretty big investment chunk.
Also, I have no idea what the rest of your system is comprised of.
I would only caution, depending on your musical tastes, that the end result might not be as dynamic as you would like to anticipate. ESPECIALLY if your tastes run toward Heavy Metal, Rock, and the like. "CICO"!!
Using the SOPHIA tubes "MAY" yield subtle or more sophisticated improvements. All of which tend to be more evident if you tastes run in the direction of classical, jazz, or small ensemble music.
SOMETHING TO THINK ABOUT.!