Can a Quality Full Range Speaker be the Limiting Component in a system?

I'm not sure where to begin...there are so many terrific responses and I'm learning with each one.

So rather than respond specifically, let me thank all that have posted. 

I wish I could have provided a more concrete situation and phrased the question better...perhaps that will come in time as I digest what you have already shared and reflect and process the points all of you have made.

Thank you.

Al, the problem with assessment of speakers by headphones is that there exists as much variance of performance between headphones as speakers. You would need a set of several headphones to peg the performance of the headphones if they were to be used as a measure of the speaker performance!  :)

MHO...no.

The physics of the speaker preclude 'accurate' reproduction over a bandwidth that relates to the range of human hearing.  Now, by 'accurate', I'm referring to a 'ruler flat' line that would appear on a piece of test equipment.  These devices Do Not Exist.  If they did, we likely couldn't afford them, nor would we 'like' what they sounded like...IMHO....

We're so used to the 'coloration' of the various drivers available, and that of the equipment and hardware that we employ with them, that 'accurate' exists in the mind and ear of the beholder...IMHO.

Note that I haven't mentioned the space in which an audition would occur.  That's an entire issue unto itself....

All of this reminds me of the 'ideal pulsating sphere' as a reproducer....which leads to a plasma 'driver'....which is only practical if you don't mind not breathing or fouling the atmosphere on a regular basis...

To be fair, I like the concept of the full-range single driver.  But, most of what I've seen and heard is still short of the goal due to simple mechanical and acoustic 'fail'.

You 'can't get There from Here.'  You might get 'closer'...but No. 

Sorry...

@asvjerry 

"We're so used to the 'coloration' of the various drivers available, and that of the equipment and hardware that we employ with them, that 'accurate' exists in the mind and ear of the beholder...IMHO."

Jerry, fully agreed. So, I say find what mix of components that make sound you like and enjoy the music.

I haven't found my speakers to be the bottleneck. Been running Lowthers (with a sub) for a long time & still hear a difference (improvement or not) when replacing electronics, wires, feet, etc. I have these so zeroed in now (which took a lot of time) that I have little desire to start over with different speakers. Just my experience...