The thing about the K4..you can use it in so many ways,,setting up to meet your sound needs..The EQ changes things in a major way..Same with the tubes preamp..and even how you place the K4 on the floor..
In the standard straight up position[like a fender twin]..is a good all around sound...

Placed on it's end...gives the most bass and punch at higher volume levels...

And tilt back wedge..fills just about any room with plenty of sound..

I can easily see why maybe a novice user would return it, not knowing what it is capable of producing..