old vs new

You are making sense, but to take advantage of this realization, you need to do a hell of a lot of research.

After which you will find that the truly great older items (as good as or better than the new stuff for half the price?) are just not coming up for sale because people hang on to them forever almost ;--) I waited two years for a Levinson 25s phono preamp and paid about 20% more than I should have -- but I just didn't want to wait another two years! It was worth it though because now it matches my 26s preamp, AND, we must remember it cost 7K 10 years ago and I only paid 2.8K for something that would cost at least 10-12K to duplicate with a new product today.
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Thats what I thought. My cousins 20yr old maggies sound so much better than some of the 'expensive' new stuff i'v heard.

Interesting question and no easy answer I think. I always buy 2nd hand but not 5 to 10 years old. Most boxes loose 1/3 of their value leaving the shop, so you still get great value nearly new. I was discussing this with a UK dealer I really respect and he says he despairs that nowone listens to his advice and that some kit has come on leaps and bounds in the last few years. For example, the Unison Research Pre amp he feels at about £1400, is as good as £4000 units a few years ago.
To answer your question, go for in demand kit less than 2 years old, you should be able to resell at mimimal loss. For example, I bought a Lavardin IT a year ago which is still worth what I paid for it. The great advantage is low risk, buy new and if it is a mistake, you have made a big loss, 2 years old, minmal loss.