You're thinking of old time "High country" close-singing bluegrass (by your description; I haven't seen "Titanic"). If that's the case, you want Bill Monroe, the earlier, the better (although with Scruggs and Flatt, you can't go wrong either.)
My grandma was in a bluegrass band for most of her life! She played the mandolin. I know absolutely nothing else about bluegrass but if you're ever in mid-eastern Ohio and come across an old String-A-Longs cassette, that was her band!
This isn't really "traditional" bluegrass, but this band is one of my faves: White Water Ramble. (Too bad you can't see the mandolin and violin "dueling" there... man they have a great time performing!).
Their music is described as "high octane dance-grass," and it's really fun.
I was also going to mention the Oh Brother, Where Art Thou? soundtrack. It seems to have lots of that old school folk and bluegrass you seem to like.
i sometimes listen to the bluegrass station on comcast. you know, those stations that are like on channel 940 or something like that.
if you don't have the soundtrack to oh brother where art thou (as others have suggested) be sure to run and get it.