I don't think the 140s are as loose on the low end as octavas, though I don't have much experience with the octavas. The 140s to me really are just a little loose in the lows, not really pronounced, just not what I'd describe as taut. As to mics with a tighter low-end, as I said above, the Milab VM44's. Having run both, I find the Milabs to be similar in sound to neumanns, but with a tauter low end and more detailed highs. The more detail in the highs is sometimes great, but OTOH can sometimes be too much and end up sound too bright depending on what you're recording.
Jason -- I think the Gefells suffer wrt taper sales by not having active cables/caps. For right or wrong, it doesn't seem tapers start spending for the really expensive mics unless they are either multi-pattern LDs or are active cable SDs like km140s, schoeps cmc6/4x, DPA 4022, etc. I know personally it stopped me. By the time I found out about the great sound of Gefells, I had moved on to active capsule systems.