Absolutely the best KT90 ever developed.
The Electro Harmonix KT90 is a great sounding tube. The low end is not boomy at all, but quick and responsive. Female vocals will be noticed with tube. Very realistic mids with a sweet top. Highly recommended.
Electro-Harmonix tubes are all new designs and are of excellent quality. Many OEMs use relabeled Electro-Harmonix vacuum tubes in their amplifiers. If you want great sounding tubes at a very reasonable price, then Electro-Harmonix tubes should be on your list.