Best Audiophile desktop for under $2500?

As folks have pointed out, the issue with the question is the word audiophile. No, no chance this will happen for either $2,500 or with a PC involved. Doesn’t mean you cannot get enjoyable sound out of it. I enjoy my office system.

Given his current system was a Microsoft OS based machine, I would doubt he now wants a MAC. I would never buy a used PC. If open to a Mac book, you can run it on batteries, which I used to do for my streaming (sounded terrible compared to any real streamer).

But you can get decent sound out (enjoyable to listen to) with a good sound card, lots of power conditioning, and good amplification.

So the real question for OP is has anyone a PC recommendation? I have a huge tower that I made, 14TB, water cooled, but very expensive. With all the space inside it sounds OK for my office system.

Cant do a MAC. Need Windows for work. I also sometimes use the PC to DJ also... like Serato, Rekordbox, & VirtualDJ. These programs need some good specs to run smooth.. But that's not my biggest concern.. would be nice to use it for that also though. The Matrix Audio Element H USB 3.0 Interface card isolates the USB signal and uses a separate power supply. This needs a PCIe x1 Gen2 Interface. It makes a significate difference.  So if there is some kind of fanless.. or quiet enough fan PC or Mini PC.. that might work.. but needs to handle a decent workload. I still like the idea of using my DELL as a server considering its one less expense. The OPPO outputs HDMI when playing movies or multichannel audio. But when playing hi res audio like 768khz, then I would need to switch to USB and use the PC HDMI. So the PC would need at least 2 HDMI outs. One to the OPPO and the other to my projector. 

Using a computer in an audio system can be as good as anything else mentioned here. You just need to do it correctly.

I posted earlier about my $5k fan less PC. I run 6 monitors of it and it is a powerhouse machine. It does not make a peep of noise. However, that is not how I setup my streaming, I use a $500 DELL machine that is the size of my hand. I have it kept under a bed in the adjoining bedroom to my office. I have perfect streaming throughout the house from this little machine running ROON Core. 

Fibre cable (glass) is your friend in this scenario. My setup needs a bit of computer savvy to get setup and keep running. Send me DM if you want to discuss.

I have worked as an audio engineer, and currently I do high end workstation builds.  I would be more than happy to provide you with a parts list and help you find a reputable builder in your area.

Here's a link to a parts list that I put together as a starting point, I'd be happy to go over the parts selection and reasoning behind the choices.   https://pcpartpicker.com/list/spgmJy