Does full range guarantee bass?

Vandersteen's 2Wq is a 6db slope. It operates below resonance and requires a main speaker that will perform down to about 40Hz for seemless crossover. Also, one of the benefits of the Vandersteen subs is the insertion of the 6db crossover filter in the main amp signal path. By reducing the load on the main speakers, you get better dynamics, bettter transient response, transparency and definition from them. It is an interesting system to say the least and one that I use and believe in.
Richard Hardesty stated that you cannot place a full range speaker in any one position that will give best bass performance and best performance through the mids and highs. Something I have learned from experience. He also agrees with the Vandersteen system for best performance.
With all that said, it should be obvious that just because a speaker is full range, it doesn't mean it will give you accurate sound(something that seems to have gone out the door in recent times-but that's for another day)and bass response. A speakers enviroment has more to do with the sound than any other component. Bad room, bad sound.
It does mean the speaker will respond to an input signal at its lower frequency limits. It doesn't promise it might not consist primarily of harmonics and distortion. You don't see many speaker manufacturers talking about distortion in their speaker. Most speakers are well over 10% distortion (actually pretty good systems)at even low drive levels in the bass. Some are a lot higher than that.
As you can see, the answer to your question is a big---depends!

It depends on a number of factors.Room interaction is very important.You can get great Bass from 2-ways that amazes me. Amps also need to be matched with the speakers to get the peformance out of them.

Others here have brought up some very good points.

I went to the tube show in San Francisco a couple of weeks ago and these amp-fanatics did make one interesting point. Speakers are terribly inefficient. they even jokes that you can use a speaker as a microphone and that what you hear is an example of the ineffieiency. Of course, a good microphone and a good speaker are not designed to be interchangable, so the point was mute(not to be funny with my choice of words...).

Still, it can be amazing what a differance the source makes as i have a high-end Cd player and an excellant tube amp and, such being the case, I have done away with the pre as i don't need enhanced tone and bass controls anymore. For me, this was quite a shock.

I have full range speakers. Monitor Audio Studio 60's.
They are rated 26Hz to 20Khz. I auditioned them at a Hifi store with a McIntosh MC2102 Tube amp and the combo sounded great and had pretty good bass.

I took them home and connected them to my Proceed AVP2+6
pre-amp and Anthem MCA-50 5 channel amp. The front end
was a Yamaha s2300 Universal Player.

This set-up sounded pretty darn good and had pretty good bass. The McIntosh sounded a bit better, but only fractionally.

Next, I upgraded to Krell FPB 350 MCX monoblocks for my
front two speakers, the Studio 60's. The bass response
now was so big, I was able to turn my sub-woofer completely
off. The Krells produced deep, tight bass, and suddenly
my speakers could rattle the room like my sub-woofer used
to. Ultimately, in my system, it was too much of a good
thing, so I switched to Levinson 436's. In my system,
the Levinson's bass response was "just right." Still
deep and tight, can still rattle the windows at times
when the music calls for it, but -- for want of a better
description -- the Levinsons disappear and don't call
attention to themselves as much.

Yet, I felt the Levinsons were just a tad more laid back than I wanted. I missed a little bit of what the Krells
were giving me, but I didn't want the full Krell treatment.

I have ordered the Meitner Dac6, but I bought my brother
a Sony SCD XA777ES SACD player, used, here on Audiogon so
I threw it into my rack to make sure it worked properly.

The difference between it and my Yamaha Universal Player
is astounding. Everything, from top to bottom -- for want
of a better expression -- snapped into place. Now, the
speakers and the amps are doing the disappearing act and
the bass response is more accurate and satisfying than ever.

Lesson learned? First, your speakers have to have the
capability. Second, you need proper amplification.
Third, your front end also makes a big difference.
Fourth -- I am still using 12 AWG Copper Speaker wire
and $15 interconnects and I have amazing sound staging,
excellent detail and focus, and extremely satisfying
high and low end extension. My advice: Don't be another guy with speakers rated only down to the 40's, trying to produce bass with expensive cables. Or, another guy
with full range speakers, but without proper amplification, trying to produce bass with expensive cables.

Speakers will never reproduce what does not come to them. Everything up the line from the speakers is more important, but the speakers are still very important.

If you have a full range speaker and are not getting good bass something is wrong with the speaker placement. That is assuming you have good electronics capable of plumbing the sonic depths. Check out http://www.rivesaudio.com for some good ideas.

The process is not that difficult. Finding the right combination that meets the prejudices of the listener is much more difficult. I think people are generally more interested in sound they like rather than accurate sound, but that's another thread.