I can't answer your whole question, but I've tried Pour Monsieur, and I agree, it's really nice - smooth and distinguished. But I don't own it, and I haven't managed to find the Concentree to try.
Something I just noticed... a new feature for this board, apparently... "Similar Threads" down at the bottom. Could be quite useful! That's where I found this thread that seems to indicate possible low longevity; that explains the Concentree, I suppose.
There are a couple of guys who have it in their swaplist. Maybe one of them would sell it. Bunch of people decanting it too! It's running about 30-40 on Ebay - that's not too awful bad