I ask because I'm looking for my next bass - I play mostly jazz but a bit of amateur orchestral as well and would love to get some huge sub-E notes going.
I remember seeing a Russian Orchestra playing a Shostakovich Symphony (4th I think) in London and the basses were nearly all 5-strings and at/near the end, there is a sort of pedal played on low C by all the basses, which was one of the most awesome sounds I have heard in the concert hall!