Actually, you didn't. So let me define it. It is a processing device that:
1. Organizes the contents of a files located on other devices into an organized local library.
2. Provides support (local or remote) for accessing those files and sending them to a DAC.
IMHO, there is no effect on subjective sound quality as long as (a) there are no data conversions, (b) the CPU/RAM is capable of the bandwidth, (c) the output connection is capable of the bandwidth and (d) the server, itself, is sufficiently quiet and isolated (both with regard to audible and electrical noise) from the the connected devices.
There is more going on. Data can be handled in 24/32 or 64 bit, it can be passed 'straight through' or messed within some way. The amount of noise in the power rails leaking into what is basically an analogue feed (USB/Ethernet) to
But, you haven't heard it so you're judging its sound quality based on no data. As for building a DIY server for under $4K, DIYer have been using that argument for years and most fail. I can build a DIY amp, or DAC, or speakers for a fraction of the cost from a Wilson, Pass or TotalDAC, will it be as good? Likely not. Net is - you are greatly underestimating the benefits of design engineering, validation and experience.
Also, I have Roon which has gotten better over the past handful of months but to my ears HQPlayer oversampling or not sounds more realistic. HQplayer is not just about oversampling, it has many filters, dither types, upsampling and PCM <-> DSD conversion. I haven't heard anything better and I've tried many.
I think there are 2 subjects here.
1. Data manipulated with either or both upsampling and filtering
2. Data sent as is (no manipulation) as bit perfect, same bit depth.
That is why I challenge why any server needs to be over 4K, to do what exactly?
On HQ player, I don't want or need any filtering, upsampling or data messing with, as I said. So in my case HQ player is not an improvement over Roon on sound quality. In your case it probably is as you clearly are doing processing of the data to affect what the DAC receives.
I will get some more demo's organised this year, and in fact are looking to distribute some for Spain. If any I find are improving the sound beyond what I have now, then that is great. But I still question why any music server needs to be above 4K.