I am familiar w/the sound of both neumanns, and find them pretty much the same (though, never done a head to head comparrison).
if anything, the 184's sound a little more sparkely to me and the 140s, a little darker, but both sound very, very similar. Probably to the point that I doubt I could pick one over the other in a blind test.
w/the 184's being about 2", or less, longer than the capsule and active cable end together, I see it pointless to spend 2x as much on them.