The Six Pac's, with the stock EL34's, does have more of a focus on the midrange as compared to frequency extremes. However, I would not say it is the amp but more of the nature of EL34 type tubes. With this in mind, you may wish to understand the "sound type" of various tubes used in tube amps before deciding on an amp. You should also demo a few amps before deciding, you may find that tubes are not for you.
Regards,
Regards,