There are going to be people like boomerbillone everywhere. Not everyone is going to be chasing the best music server and for him, a general purpose computer is more than good enough.
That being said, if your system has the resolution, you will be able to notice significant differences between computer / music server and power supplies. I built my own general use computer for my office computer / audio system because I need a "general purpose computer". I play music, do a lot of gaming, youtube videos, photo editing and work on my system. Currently, I’m running a stock Pink Faun S/PDIF PCI audio card on an AMD processor motherboard (with multiple sets of mirrored SSD drives and video card). It uses AES/EBU cable to connect to a higly modified LKS MH-DA004 dac. I can definitely hear differences in sound between powering the Pink Faun card using the internal computer switching power supply and an external Farad Super3 linear power supply. With the computer switching power supply, you can hear a lot of distortion and noise in the audio signal and the sound just does not have as much "oomph" and resolution when compared to the external Farad Super 3. The Pink Faun card is awsome becuase you can upgrade it with a high end OCXO clock, but it is definitely expensive.
Now you can take this further and compare my computer with a dedicated high end music streamer/server, such as the Aurender or Auralic models. I have not done this, but I suspect that the Aurender/Auralic could very well sound better than my computer. They have fully linear power supplies with hardware that is selected and designed specifically for only doing music streamer/server duties. They are NOT a "general use computer". You don’t have to have 32GB of ram with expensive 10-core cpu and hard drives with video card to be able to do what a music server does.
There have been people who have been very succesful in building a music server from a computer platform They generally have fanless cases and cpu heatsinks with linear power supplies such as HDPlex. You are not going to get a super processing computer because the linear power supplies pretty much max out at about 500 watts. If you need to do gaming and processing, web browsing, business, then a general purpose computer may be what you need.