How much does a Zobel network and its components affect the sound of speakers?

" The edginess is minor and infrequent and not an issue I’m particularly concerned with. I mentioned it in passing. "

I misunderstood and thought that was the issue you were working on; sorry about that.

Duke

Audiokinesis... no, "my bad." Thanks for your input about off axis energy, I'll check it out.

"Moreover, why has Merlin Audio (now defunct) experimented with their network components, before settling on the Dueland/Caddock combo?"

@pmboyd Bobby used a Hovland capacitor in that position before switching to Duelund. He mention to me at an audio show that the Duelund cap in the Zobel was a significant improvement. Its low .01uf value in the Zobel was a relatively inexpensive upgrade and did not much upset the overall price point of the speaker. He also used cryoed Caddock MP resistors and Hovland mylar capacitors throughout in the crossover. If you want to improve the speaker, consider replacing the Hovlands inside with better parts.

I considered that but it's an expensive upgrade, expensive enough to consider replacing the speakers altogether, not least of which because of the time required to open the sealed enclosure and remove and replace the extensive bracing. Instead, I thought it might be worthwhile intestigating replacing the Zobel as a inexpensive alternative. I'm generally pleased with the speakers, but want to get a sense of what the Zobel with its potential components contributes to their sound.

as "AK" mentioned sounding edgy at higher volume could mean a high amount of off axis output but there are many other potential causes.
I review of your speakers mentions the need for precise room positioning and toe-in.  This also implies that the listening position needs to be somewhat nearfield and also dedicated as lots of true monitor speakers require.  
Does it sound edgy while walking about or in different listening positions other than dead center?  They are designed to sound best listening dead center with considerable distance (4 feet or so) from side walls and optimized toe in.  
Getting the speaker and listening positions at their best is important for these speakers.