Why do Harbeth speakers have such a cult following

IMHO, speaker sound is very much a personal preference. I've owned many brands of speakers over the 40 year period I've been a hifi addict. I still have fond memories of my first speakers, KLH 6s. Now that I find myself in a small apartment, the Harbeth 7ES-3s sound excellent in my bedroom. I especially like the fact that room placement isn't a major issue. While I listen mostly to jazz, I occasionally play rock. My Harbeth's make any kind of music sound great. With a good recording, they will sometimes put out low frequencies with such power and realism that it's scary. I agree with the person who said that they do better with gobs of power. I think that class A equipment would be ideal but it's expensive, gets hot, and will eat power. (I know some of the new class A amps have circuits that reduce heat and power consumption without  intermodulation distortion, but they're out of my price range.)

If anyone knows of speaker wires that compliment Harbeths, would you be kind enough to let me know?

I have used Audioquest Rockefeller speaker cables for 4 or 5 years now. I just switched from C7es3's to SHL Plus as of 5 days ago and they're still a match made in heaven for Harbeth's. 

I've used Acoustic Zen cables (Double Barrel Shotgun and Absolute) with Harbeth SHl5+, feel like they are both a great match. 

If you were forced to eat bangers and mash, you'd like Harbeths too

Obviously you've never eaten bangers and mash. There's never been a forced eating on record. Too delicious.