I don't know what's best , but at least this is worth reading .....
http://www.borbelyaudio.com/15wse.pdf
(scroll down to page 3.)

"Grant Sellek" schreef in bericht
om...
Hello everyone,

is there a way to slightly increase the second harmonic distortion of
a SET or similar single ended amp? Should it be done in the driver
stage or the output stage?

If you are thinking of reducing NFB, what if the amp has no NFB?

I simply want to experiment and find what differences I can or cannot
hear. However, I want to do it in a way that leaves the amp performing
at its best in all other ways.

Thanks for any help,
Grant