First of all, this price was attained using Micro Center's sales and a used graphics card. If you plan on building this exact configuration at retail prices, the price will probably be a bit higher, but you could choose a cheaper case/RAM/Fans to stay within $500
CPU: Ryzen 5 1600
Was able to get it to 3.85 GHz @ 1.3V. Extremely happy with the performance that this CPU gets for $80 including the stock cooler.
Motherboard: ASRock B450 ITX AM4
Got it for $30 off with the CPU/MB combo from Micro Center, pretty capable board, and overclocking potential was enough for me. I absolutely despise AsRock's RGB program as it is extremely glitchy and unable to find the RAM in the software.
No complaints, clocked at 3200 MHz and works with ADATA's RGB program pretty well. The "liquid-cooling" doesn't actually do anything, just a gimmick.
Graphics Card: Gigabyte AORUS RX 580 4G
Bought used from r/HardwareSwap. Was previously used for AI Learning, but performance has been great although I have no idea on how to change the color of the logo as RGB Fusion doesn't detect the device.
PSU: Corsair VS 450W
Kind of the lowest of the low in terms of brand-name power supplies, but is working fine in powering the rig with no crashes at full load.
Case: NZXT H200 (Black/Blue)
Beautiful case, even if it is one of the largest ITX cases on the market. Building in it was relatively easy and thermals are solid.
Case Fans: upHere 120mm PWM RGB (3-Pack)
Pretty good value for the money although my motherboard cannot get the RPM of the fans. Not sure if it is a problem with just my unit or if they are all like this. Colors are vibrant and are quiet.