Tekton Double Impacts

@strateahed , using an active sub on a full-range speaker with extended bass will provide the amp with an easier load to drive. The amp needs to use a higher amount of current to drive the low frequencies (more air to push), so if the sub can help with the low-end, then the midrange and low-mids will benefit by getting quality power from the amp with with no clipping.
If it's a large room, a subwoofer is a benefit to the sonics of the tower speaker.

I have owned the the 3.6 . .if you want real low Bass get a good powered sub Like 
JL Audio, or Rel.  Your panel is good only to about a honest 40hz at best. 
Your amp should be good wuslity and at least 250 wpc to not distort  as easy.
A good powered sub has several advantages.   For one  to take any bass  below 50hz.  It takes a big load off your amplifier,  and set to around 50hz your panel slso will be much more at ease to you. Without bottoming out.

To my brother from another mother, Mykeryte (Mike)

In the spirit of discussion about were the DI would fit into the overall perspective of reference level speakers, regardless of price, we have a honest but passionate disagreement between to listeners, professional  reviewers, and friends regarding what you hear and my experience of the DI compared to your series-1 Wilson Sashas speakers.  One big difference between me, you, and Allan is both of you love to hear music at much/much higher volume levels then I do.  This does not imply that the DI will not effortlessly play over 100dB with ease, however in my opinion, regardless of the room/system the individual players will start to sound "larger then life" which is not a natural presentation to me.  So, next time you come over I'll let you pick the volume level that sounds right for your ears.

I totally respect your love of your Sashas speakers, but historically I always felt they were one of the most over rated speakers I had listened to in many systems.  The series-1 had the Focal inverted dome tweeter which after a short while of listening to the speaker I always found it quite annoying and very unpleasant to the point of not wanting to stick around.  Finally, when Wilson could not score Focal's tweeter anymore they finally went to a silk dome tweeter and I found the series-2 Sashas a much better sounding speaker.  Even with this improvement I have always found Wilson speakers to sound like good speakers that measure great/do everything right/,except make music.  When I was at your house and heard the Lawrence Audio Double Bass speakers which you reviewed I liked them a lot more then your Wilson speakers.

I had as my reference transducers in my big rig the Lawrence Audio Cello speakers for over five years and enjoyed them, and still do in my smaller system, which retail for $18,000.00 and they were out performed by the DI!
The DI is not just great for the money, it's a reference level speaker, regardless of the cost and I believe, stated with respect, if you had them in your house you might discover they out perform your Wilson's just like they outperformed my Lawrence speakers.

 

Judging sound quality of audio products will forever be subjective by default.  There are multiple variables at play that prohibit universal concensus.  That's the beauty of this endeavor,  near endless possibilities of choices/audio products that allow one to seek and obtain the sound they want. 
Charles 

Mac48025 3-6-2017
I’m told the impedence curve also influences how hard a speaker is to drive? The flatter the impedence curve the easier it is to drive?

Yes, generally speaking. Although if the impedance stays relatively high at most or all frequencies lack of flatness will be less significant than if it dips down to low values at some frequencies. For example the impedance curve of the Enzo XL that I linked to earlier varies a lot over the frequency range, but never goes much below 6 ohms, which minimizes the significance of that variation.

Also, the phase angle of the impedance can be a significant factor in many cases. That is shown as a dotted line in the impedance plots in Stereophile’s measurements, and corresponds to the markings on the axis at the right side of the graph. Very negative phase angles that may occur at various frequencies, especially if they occur at frequencies for which the magnitude of the impedance (the number of ohms) is low, will work in the direction of making the speaker a more challenging load for the amplifier. JA will usually comment on that. For example, in the Enzo XL review he commented that "the Tekton speaker’s impedance magnitude (fig.1, solid trace) remains above 6 ohms at all frequencies, and the electrical phase angle (dotted trace) reaches extreme values only when the magnitude is high. The Enzo XL is therefore well suited for use with low-powered tube amplifiers." The "extreme values" he refers to for the phase angle are in the vicinity of -45 degrees, but occur at frequencies at which the impedance magnitude is around 10 ohms or more.

Regards,
-- Al