I have had the AHB2 many times over the past decade. I no longer have it but I did a lot of speaker cable comparisons before I sold it. Mainly because the AHB2 was the best amp to hear the gear.
The speaker cable that Benchmark sells is really good for most systems. If the system is highly resolving, then you will hear the limitations on the BM speaker cable. I heard this with cables costing $7K to the $100 BM cable. Though the issues were evident at different frequencies with each of the cables. The BM cable is what I would use if you cannot hear the BM cable gremlin in your system. I used it for years in my office system which was not uber revealing.
My favorite speaker cable is the Audience FrontRow cable. I got those terminated by Audience with the SpeakON connectors and used them with the AHB2 and headphones. I also used a customized CODA #8 amp with this cable and headphones. I could not hear any improvement in the sound with the regular spade or banana speaker cables with either amp. I now have 2 sets of Audience FrontRow with non-SpeakOn termination and both amps were sold.
With power cables I could not hear any change in sound on the AHB2 and the stock cable vs audiophile PC’s. Now I do not have anything extravagant to test with, but I could not hear any difference with the cables I had.
I also found no difference in sound using the BM stock XLR’s between my BM HPA4 preamp and the AHB2. The XLR or RCA into the HPA4 made some difference but nothing major. For example, a tuner into the HPA4 sounded mediocre with a cheap RCA into the HPA4 but an Audience AU24 SE RCA made a positive improvement.
I wonder what Benchmark’s response would be if you asked them about a power cord upgrade? They know their products best.
Answer from Rory Rail at BM to me was don’t waste your money with a non-stock cable for the AHB2.