Yeah, Rashomon is great, when it was first released via RKO, there was a dub in the US, but just try and find that dub on DVD now, it's not that easy.
It's hard to find English dubs of any foreign films these days, I guess a 'popular' action film like Crouching tiger gets a dub on the DVD, and plenty of American films get localized dubs in other countries, so I guess it has to do with the children-and-lazy-teenager factor in both cases. I think Hollywood finds it more profitable to rip-off and remake the original films and completely Americanize them rather than honestly importing foreign films that might appeal to the mainstream.
I don't think you have to be "hardcore" to shun dubs, you just have to appreciate watching the work of the original artists; the real juice, not from concentrate, not filtered or watered-down. Which is why I think anyone who could truly call themselves a "fan" of any given series/film, can't also prefer the respective dub over the original, I doubt they could even tolerate it.