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

If the question is referring to full range speakers meaning full range single driver speakers, some of the higher end Lowther drivers claim a 20Hz-20KHz frequency response. So I suppose they technically exist. Same for full range speaker "systems". So the question then becomes a measurement issue as whether or not every component in the audio chain can deliver the entire frequency range. If so, then theoretically there's no bottleneck.
The problem is if we mix the notion of the sound quality with measurements, then the discussion becomes completely subjective and there's no single answer to the original question. 

@inna I’m actually referring to prices as new and yes they are $50k speakers in a $500k+ system. Magico Q3s actually. My point is that decent speakers at this price level are capable of really great performance if matched well, and I’d rather invest in better sources to get more information for the speaker to work with (call me Linn school) .

In addition larger speakers would overpower my room, I could go to M3s for example (and probably at some stage will) but anything bigger would cause me so many problems

So back to the OPs question if your speaker is showing you the impact of changes elsewhere in the system, and if you can work within the frequency limitations of the speaker (for example mine may not have everything in the bottom octave but the acoustic design of the room helps here) then don’t go chasing a speaker change which will likely throw the rest of the system out of kilter

Speakers overpowering the room is an excellent reason not to have them, agreed.
I am a Studer school too, folkfreak, but probably not as much as you are. $50k speakers in $500k system - no, but $5k speakers in $50k system - no way. $50k still buy a lot of a speaker.

I would do bigger, even much bigger speakers in your room. You have the potential, if you wish, to put a rig together that would humble the current one, but it would have to be with greater transducers. Could be done easily with the means and desire. I would have a 6' speaker in there and it would sound glorious.  Everyone has differing priorities; I'm just saying that if I owned that room I sure wouldn't stop at a smallish speaker.  Imo, too much handed away, regardless of the pedigree of components.  :)

I think there is some confusion here, I assume David meant a full range "speaker" meaning a loudspeaker with presumably multiple drivers. It seems that some are assuming he meant a single full range driver. David can you clarify what you meant because those are two very different discussions. Thanks!