My Rythmik subs have variable Q. Seamless integration (to my ear) was often possible at more than one "Q" setting. Sometimes, my preferred Q setting changed, depended on other x-over variables (like slope and and x-over frequency). And, even though seamless integration was possible at different Q settings, the overall character of the system definitely changed, depending on which combo of Q and other parameters was chosen.
Generally speaking, I found that it is definitely possible to "mismatch" the Q of the sub and main speaker (when it's wrong, you'll know it), but there is no one perfectly "right" answer. I suspect that some degree of experimentation is probably useful to optimize Q to personal preference. I would personally recommend a sub with variable Q for this reason.
Marty
Generally speaking, I found that it is definitely possible to "mismatch" the Q of the sub and main speaker (when it's wrong, you'll know it), but there is no one perfectly "right" answer. I suspect that some degree of experimentation is probably useful to optimize Q to personal preference. I would personally recommend a sub with variable Q for this reason.
Marty