Does Gryphon Diablo 300 Benefit With A Costly Mains Power Cable?

No experience with the Gryphon Diablo 300.  However, one thing I do know is, with any amp or other components, trail and error is the key to finding the perfect power cable for that particular component.  Happy listening.  

Why not give Gryphon's Vanta cord a try?  Maybe your dealer can arrange a loaner.

audphile1, looking for better clarity and separation, a more open and larger 3-dimensional soundstage and perhaps a brighter and more dynamic sound. 

It’s true, trial and error is the key. I have been swapping power cables between components, wall to power conditioner and conditioner to components over the past few years, and the differences are clear. What I have found is the best sounding (usually costlier) power cable should go between the wall and power conditioner for the best result, not the other way round. 

I didn’t notice the existence of the Gryphon Vanta and will look at it. I did try an older version of the Gryphon’s speaker cable when the dealer brought it over and although it did sound different from my current cable, it wasn’t exactly an improvement and I have no urge to own the cable after the comparison. 

Most amps will benefit with a Not Necessarily Pricey replacement power cord made for audio gear. You can find some on Amazon for under $100. I have five of them and they work well. If you examine their constructrion, you'll find they make the wires fit differently inside the insulation than ordinary, standard issue, power cords. The primary aim is to prevent the cable from picking up and conducting radio frequency signals into your equipment which was never designed to remove RF signals which might make it through the filters in the equipment designed to remove the AC frequency 50 - 60 Hz and nothng more. You wouldn't think stray radio signals would have any effect on audio gear, but they do. You may have noticed ads boasting frequency response flat to 1 or 2 MegaHz. That gear needs serious protection!  They don't have to be expensive. 

Does Gryphon Diablo 300 Benefit With A Costly Mains Power Cable?

In a word, no. Nor does any other component benefit objectively from a power cord, interconnect, etc.