When I bought my ProAc Response 2's 25 years ago, they came with matching custom-made MDF stands that looked wonderful but sounded awful. I finally found a used pair of Sound Anchors, and it wasn't until then that I was able to stop fiddling with the speakers and really enjoy them. There's no question in my mind that speaker stands make an enormous difference. Personally I would take the manufacturer's recommendations seriously if at all possible in terms of space and available funds. It would strike me as very odd if a company as old and reputable as Harbeth were promoting "snake oil" solutions. They have every interest in making sure their customers hear their products at their best.
Do different speaker stands can really make a big sound improvement?
I am looking for stands for my new Harbeth P3ESR XD speakers and wonder how much improvement one can actually hear between close to a $1000 stands and a $100 one filled with sand?