Best Audiophile desktop for under $2500?

Presumably you are feeding the PC audio out to a external DAC to an audio system.

Based on advice here, I switched from simple headphone audio out jack (using pc's DAC, lousy) to USB audio out to DAC (far better) to Luxman Integrated Amp to Darn good sounding Speakers (more important than the data/dac). World of difference.

I had poor speaker location for many years, totally revised my office for seated ear level, centered seating and could not be happier.

I don’t stream separate audio, just Music Videos, YouTube/Smart TV netflix/prime/viki/paramount .... shows, some here in office, most in Home Theater AV Receiver Downstairs. Most pre-recorded, watch without commercials.

Real Dolby 5.1 sources, OR, turn default pseudo surround i.e. 5.1 off, use 2 channel stereo mode, i.e. DIRECT finds 2 channel original, or forced 2 channel. VERY often better sound.

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In the office the PC fan(s) and Hard Drive(s) Noise can be as/more important than the digital audio output performance.

For that reason I buy HP compact PCs with both audio and video on the Intel motherboard, no fans, and Solid State drives (no noise). My PC Processor’s fan rarely comes on, and is whisper quiet. Leave proper/extra ventilation to minimize that fan or any extra fans to run.

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Intel 730 on the motherboard

Processors are so fast, they have for a long time been waiting for you. Gaming a different world.

Wouldn’t the OP be better served with a server/streamer than a noisy PC? Is the DAC the Oppo 205?

Look into what I posted about the Sonore OpticalRendu or even the non-fibre Rendu's. They will allow you to keep your computer far away from your music system (several rooms away).  If you use fibre, who cares about how noisy the internals of a computer are. That noise will not travel inside the glass fibre cable.

kennyc

you are probably correct about the server/streamer, but the OP needs a new computer, so he wants to choose based on member's experience with their audio quality. 

If you stream Video like I do, the audio is originating thru the PC.

If the Op wants to stick with a PC then I'd suggest a small form PC that has no fan and an external power supply. I used an optimized for streaming Asus vivo that proved to be better than a $7K streamer.

The small form fanless PC's remove the power supply from the housing. This helps with that noisy power supply and gives you options to improve the power supply. Optimizing the PC for music streaming is also advisable.  I used the Optical out but most modern DAC's have good galvanic isolation for USB now so that's not an issue anymore.

This is the thing most good DAC's have good isolation / correction of data streams etc. and I'm finding streamers to be less critical as DAC's improve. 

I've done the Optimized PC - Roon Nucleus - Aurender A10 - Chord 2go/2YU (current, I have a chord DAC) and potentially going back to an Optimizes PC. granted I have a monitor/TV in the same room and a wireless keyboard with a track pad so that makes things easier. 

To me the DAC is far more important now then the streamer attached.