Early on I directly experienced the effects of relatively small changes within computers/streamers. I started with laptop then went to a series of three Mac Mini's. First Mac Mini started stock and then I began to optimize via disabling various functions in operating system, result was small gains in sound quality. Next Mini had more powerful processor, went deeper into optimizing operating system, this to extent of going into DOS to disable even more functions, result better sound quality. Third Mini, even more powerful processor, extreme optimization of operating system, modifying to two hard drives, later to two solid state drives, conversion of Min's internal switching power supply to linear power supplies, this with two different iterations from different manufacturers, again all this resulted in sound quality upgrades, linear power supplies having the greatest effect.
And so I directly experienced via diy all the things commercially available audio streamers do to convert and optimize what in most cases are general use computer motherboards into high quality audio streamers. In general what we're trying to eliminate is noise from all devices in streaming chain, operating systems devoted to only provide functions necessary for streaming music files, quality linear power supplies, optimized interfaces are just a few of the things differentiating computers from audio streamers. And there is so much more, depends on how much money one is willing to spend, look at the latest offerings from Taiko to get an idea of how far we can take it! A quality streamer is absolutely integral in getting best sound quality via streaming.