At what point do you...

Personally, I always buy brand new as long as I can afford it. Will buy used if the item is no longer available new and if it’s a must have for me, but mostly only in person so I can verify its authenticity and functionality or will order if it’s an item that I already have and already know what to expect and to look for. If the savings is substantial (relative to each individual) I would be more inclined to buy used from a reputable source at half price or less and only if it can be returned without hassle. I don’t have a problem overpaying for something to get what I want the way I want it. Good service merits its own price tag.

At least with cables, since it sounds like that’s what you’re interested in there’s not much to go wrong there but would be beneficial to already have a one to compare to and make sure it’s authentic. Lots of fake stuff going around...

I would never buy open box or used speakers without auditioning.  Highly likely to have been abused or damaged and a hassle to repack, carry and return.

bigtwin  One of the reasons that I avoid buying used is because some things require a proper brake in period and there is no way to know how that item was treated and if it was properly broken in.

A proper break in period will determine the longevity of an item and only the original owner knows how something was broken in. Some people take a brand-new car and rag it from day one.  The next buyer of that car will end up with a car that perhaps will only last half as long as it would have had it not been mistreated. 

So, in the end, when considering how many years it has left, would the buyer of that used car really be saving any money? No.  That buyer would actually lose money when you do a cost of ownership analysis over the lifespan of that car.

This is why I don't buy used, particularly speakers, cars or items that should go through a proper break in period, but to each their own...

bigtwin Best of luck resolving your amplifier problem.

Since you mentioned it, I bought a used SL 550 from an elderly retiree in Palm Springs, CA. a few years ago, and only because they had stopped making that model and it was the last year that it was produced and could no longer be found new. I thought it would be a safe purchase since he was the original owner, retiree and elderly. Long story short, it required multiple trips to the dealer and a lot of inconvenience and time on my end to get it up to par. It wasn’t worth the hassle to me. I traded it in for a new model shortly thereafter.

I guess my point is that the older one gets the more important time becomes, and I prefer to not to chance wasting it if I can avoid it and buy new.  Now in my late 50's my time has become more important than saving money, but I also don't waste it.