Setting up M&K V-1250THX Sub

A few months back I had to break down my home theater and put it in storage during some construction.

I think the settings on the back of my M&K subwoofer have been altered and I can't find any notes from myself regarding the settings I used.

I found the manual online, but I was hoping to get some advice to go with it.

It's paired with a Denon AVR-3300 receiver (non-THX) (and of course the rest of the V-750 THX speakers).

Going by the manual's suggestion I should set the low pass filter to 80Hz 24db / Octave, the phase positive, and the bass level to variable.

I think I had the bass level set to THX anyway, but I can't swear to that.

Should I stick with the manual's suggestions or set the bass level to THX?
Does the Denon even need to use the sub's crossover circuits or are they better?

Thoughts?

Btw, I now believe I had this set up the other way.

The Low Pass filter was set to 'THX' and the Bass Level set to 'variable' (and the dial on "Reference").

With either of the toggle switches in the other direction, the volume of the subwoofer is really weak when doing a level test against the other speakers.

In this set-up the subs volume can be kept at 0db off from the other speakers.
I don't know if this is right, but it sounds pretty close.

I still want to do a frequency sweep test(?) to make sure it crosses-over right.
I'm still open to suggestions with anyone familiar with these components.