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

My only experience with a "full range" single driver speaker was the Hornshoppe Horns. Within it's operating range it was really nice. 
Sometimes wonderful.
That's the problem. 

All the best,
Nonoise

In my experience the answer is "unlikely". Assuming the speaker is not fatally flawed in some way my experience is that upgrading the source makes the speaker sound better. I currently have a mid six figures system in which the speaker is less than 10% of the system cost yet every time I upgrade a piece of the system the speaker sounds better. No doubt a more expensive speaker could sound better but it would need re-optimizing the entire system around it. System synergy is the key and I would suspect that unless and until the room changes (bigger for example) a well matched speaker still has a lot more to give

My experience is the same. Unless there is a big room change or you want a very different sound or start listening to the kind of music that your speakers are not up to, orchestra music as an example, good speakers don’t need to be replaced.

Yes, a full range speaker, even if matched to the room and amp, can become the bottleneck, but it usually isn't.

I have been building speakers for 30 years and am a former industry member, so...

Most competently made speakers of a given size are going to work as they were intended, and the botteneck will occur elsewhere. Except in the following case:

The speaker has limited dynamic range for the kind of music and SPL you like.   Many speakers which sound fine on jazz and rock at medium levels, fail to reproduce full range orchestral music, which can have almost 30 dB peaks.

Orchestral peaks sound hard or distorted, or the woofer does not reproduce the bass tones and pitch correctly (one note bass).

Even on jazz and rock, the increased dynamic capability increases the emotional content, imo.

This is why I stick to large, sealed box woofers (10 inches or more) and multiple midranges if needed.

david_ten, there is no way to assess components of a different genre in consideration of their absolute value to each other. All such comparisons are relative. You simply have to assess the performance of a component in a system. 

What is it you are trying to discover? There is no absolute correlation between the performance of a speaker to another, nor to components. It is a complicated network and to date we cannot isolate the interactions. 

folkfreak, politely I disagree with your assessment. Your system and experience could be elevated tremendously with different speakers, or ones up the line. This is no dismissal of your fine transducers, but merely pointing out that there are always many, many rungs on the performance ladder to climb if so desired, and upgrading speakers can in a moment, even when dropped into a current rig, scale many of those rungs. Personally, if I had the means I would not opt for a lesser speaker, as too much in terms of performance/experience is left on the table. All speakers can be improved with components and cables, but you are still bound by the hard limits of the speaker's performance. The odds are very good that with a speaker upgrade even if the system is not optimized for the new speakers the sound would be perceived as dramatically/holistically superior.  

Your methodology is not wrong, unless you have the means, yet are opting for a "budget" solution when it comes to speakers. And yes, I'm aware you have Magico speakers.  Imo, regardless of the system budget, 10% into transducers is severely restricting performance. Note that I am discussing this relative to your situation, not relative to the average audiophile's system/sound.   :)