Why the fascination with subwoofers?

Sorry everybody, I posted this morning after the first page and not at the end of the thread.
This is a very timely topic for me as I am about to buy some new speakers. I have listened to both the Vandersteen Treo CT and the Quatro Wood CT at Audio Connection in Verona NJ. I was very impressed with both. These demos however were performed using John Rutan's house Aesthetix amps.
My amp is a Pass X-250.8. It is powerful and has very good bass control. I would love to bring it in and demo the speakers with my electronics but the problem is that it's so heavy to put in the car along with my pre and drive for 1 1/2 hrs to Audio Connection to do a more proper comparison between the two speakers. Also, my wife and I will be moving in a couple years when she retires so my listening rooms will change over time.
My two questions are:
1) Is it better to get the Treo CT and add a Vandersteen sub that can be positioned in appropriate locations as we move or just get the Quatro CT and not bother with subs?
2) What's the consensus on adding an AR REF 6 pre in the future to compliment my Pass amp, or could anyone recommended a different similarly priced preamp?
Thanks so much for any advice.
Bruce

Why do you think you will need a subwoofer with any of those Vandersteens that you auditioned at Audio Connection? I use a subwoofer with my small stand mount speakers that only go down to 75hz. I would think those full range Vandersteens would not need a subwoofer!

I am a former AudioKinesis owner and really respect Duke's work. His Swarm is a great system. I took a similar path as I wanted smaller drivers and boxes. I use 8" drivers in 0.4 cu. ft. sealed boxes. The four boxes sit at various spots in the room. I use a Beveridge RM-3 active crossover with LP and HP boards cut at 100 Hz, Linkwitz-Riley 4th order 24 dB slope. Amplifiers for above 100 Hz are either Atma-Sphere or Music Reference, the bottom a vintage Luxman. I use this set up with my ESLs and box speakers and all I can say is I wish I did this a lot sooner. I can't see going back.

@brskie,
I own the non-CT Treos, and have 2 2wq subs. I am very happy with the combo. So much so, I will probably get the new Sub 3's when I sell the 2w's.
If it were me, first I would ask Johnny.
Barring that, I would think getting 2 Sub 3's with the Treo's might possibly be a smidge better than the Quatro's(as you can distribute the bass within the room)- Only if you have limited room/placement options-which is my problem.
The Treo's are a tad smaller than the Quatro's and I can place them easier in my cluttered LR/DR.
As far as amps go, the Pass should be a nice match. I have no experience with AR.
One thing I would offer is that Vandy's like zero feedback amps.
I use Ayre and Atma-Sphere.
Bob

@yogiboy ,
Vandies don't 'need' subs, but having them really fleshes things out, subtle but noticeable. Quatro's have built in subs with equalizer.
B