Best Audiophile desktop for under $2500?

Let's not forget, PC for Music Videos,

you don't get them thru audio service streamers do you?. They are the Primary Source of 'streamed' content, my PC with a lot of memory and fast processor/ 27" monitor DAC, Luxman Integrated/AR-2ax

I also stream music videos, music tv on my Home Theater, laptop's not gonna cut it.

I do not understand why so many want to tell OP what he wants is wrong, do this instead. 

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.