If the only mod to the normal PC is the JCAT USB card, the Lumin streamer may sound better. My post here is what I’ve experienced on my recent journey of learning about streaming audio to back up my thought. Warning: I'm a novice and NOT any sort of expert.
Some background: I prefer, at this point, to use a PC for my digital audio source since I use a streaming service (Tidal), but also enjoy YouTube selections for music (for example, live performances of various groups and I’m a drummer, so I enjoy watching drum related videos, etc.). The PC’s HDMI video output is connected to a large screen TV and is also great for using the desktop version of the streaming service software.
Before modifying my PC, I connected the USB from the PC to a USB input on my DAC (more on this below) with a reasonable Wire World USB cable which was a large audible upgrade, mostly in bass response, from a $6 USB cable that was my original connection.
I took a run of the mill Dell desktop PC and did the following upgrades, one by one and noticed improvements with each upgrade / step. This PC is only used for streaming. I don’t check my email on it, don’t do any CAD drawings, don’t run QuickBooks on it, etc. I do not store any digital audio files on the hard drive either.
Before using my PC as a streaming source, the i5 processor equipped PC was wiped clean, then a fresh load of Windows 10 Pro was loaded. All unnecessary apps and software were uninstalled. The power supply was replaced with a $150 Corsair power supply with a fan that only runs when needed. For the majority of my use of this PC, the power supply fan is not running (low noise). The hard drive is solid state, which is silent in operation.
I’m using a McIntosh C53 preamp with an internal DAC (DA2 for the McIntosh followers) and there is a downloadable file from McIntosh’s website that once installed on my PC, cleaned up how Windows handles USB audio. That in itself was a big change due to how poorly Windows handles USB audio, though this may be irrelevant in your situation.
My first hardware upgrade to the PC (besides the computer’s power supply and the better USB cable) was the JCAT USB Card Femto with a Topping outboard 5-volt linear power supply to power the USB card. This upgrade was a nice increase in sound quality; smoother, better low end, seemingly wider soundstage, etc.
2nd upgrade was to ditch the onboard WiFi and hard wire the PC directly to our decent $350 router via ethernet cable. I’m not sure if there was an audible improvement.
3rd upgrade was to replace the generic Cat5 ethernet cable I was using with a shielded Cat8 cable of decent quality. One would think the ethernet cable would not make a sound quality difference, but this upgrade was definitely audible.
4th change was to use Fidelizer software (not the free version, but the $70 version) which runs at every boot up or restart of the PC. Not sure if this helps, but there was some intangible aspect to the system that I preferred listening to the system with this software running. The jury is out on this one, but I have not removed that software either.
5th change was installing the JCAT Net Card Femto. Another very audible improvement and worth the money. This card is also powered by the outboard linear power supply and not the motherboard.
Still on the list is to improve the USB cable and potentially use much better outboard linear power supplies.
Many people on these boards advise not to use a non-modified desktop PC or laptop for streaming music. I would agree based on what I experienced by starting out with streaming music from Tidal using non-modified laptops and desktop computers. The upgrades I did certainly increased my enjoyment of streaming music, especially the JCAT cards which provided the largest improvements along with the upgraded USB cable.
Disclaimer and YMMV: I have never owned a dedicated streamer to compare my modified PC to, so take my info with a (large) grain of salt. I’m not an expert on this stuff either; I’m at a novice level with digital sources and I’m sure that is evident while reading this. However, I have done quite a few A/B comparisons of tracks and albums using my McIntosh CD player and the modified Dell PC. The CD playback is via transport only using the digital co-ax output from the player to my preamp’s DAC with a reasonable Kimber digital audio cable. I prefer the tracks/albums via streaming on the PC verses the compact disc, though the difference is slight between CD and the PC sources.