I think the best soundalike I've heard for Vader was on the old French versions. They did a really good job casting whoever that was. I dunno if it's the same guy on the home releases or what, but anyway, back before I had a VCR and all that jazz, I'd just watch it anytime, anyway. So when it came on the French channel, I'd watch it there.
One funny thing is that in A New Hope, they called Chewbacca "Chico" when calling him by his nickname. He was "Chewie" in subsequent versions.