This is why I don't like this seller (See below). The beauty of an amp that will take various power tubes is an asset because you can tailor the sound as you want. If the amp IS designed around a particular tube then possibly it will sound best with that power tube however, given that some PrimaLuna owners like KT series tubes over EL34's then they can use those particular tubes. This is why I don't like USA Audio bashing other companies.
Copied from Mingda ad:
Any tube amp that can run any every tube available on the marketplace, as some competitors claim, is an inferior design - for example, an amp will either be a EL-34, KT-88, a KT-120 or KT-150 amplifier. Do not buy in into the myth that all tubes are created equal and any one amplifier can run them all.
If that were the case, we would not have a myriad of different tubes for many different applications and performance.
An amplifier that can run any tube is an inferior design. It would be great to be able to use diesel and regular in your automobile, but you don't, because it will not work.