First real quick, you have two NF-P12 fans, case only supports one fans.
I have built multiple builds in the SG-13 and believe it is by far the best SFF case under $100, to get better I think you have to step up into the $200+ range of the Ncase/Ghost/Dan Case/Sliger etc...
Based on you list I think there are trade offs that could be made and have a better gaming PC/general PC. I have built a list bellow on what I would build at the same total cost in your list, the main trade off is the memory, is there a specific reason you are going for 32gb, if this PC is for gaming there will be no benefits with that much memory now or in the next couple of years. Using the money from the memory and the CPU change you can move up to a 1660 super,. The GPU is a much bigger upgrade about 15% on average better than the RX580, and at 1080p with either of the cards you will be GPU bound, not CPU bound, so the 3600 is a better buy, also the 3600 will age better. I would do the big shuriken 3 for the same price its a much better cooler, and I would choose the Strix B450 over the MSI B450 due to the better bios and more importantly it has two m.2 slots, in the future you could add another m.2 ssd for more storage. The PSU was more to match the build price, there is nothing wrong with the EVGA, but the corsair is slightly better and has sleeved cables so if you don't care about making it $20 higher total price get the corsair.
PCPartPicker Part List: https://pcpartpicker.com/list/9nFK7T
CPU: AMD Ryzen 5 3600 3.6 GHz 6-Core Processor ($189.99 @ Amazon)
CPU Cooler: Scythe Big Shuriken 3 50.79 CFM CPU Cooler ($46.99 @ Amazon)
Motherboard: Asus ROG Strix B450-I Gaming Mini ITX AM4 Motherboard ($138.98 @ Newegg)
Memory: Corsair Vengeance LPX 16 GB (2 x 8 GB) DDR4-3600 Memory ($84.99 @ Corsair)
Storage: Crucial P1 1 TB M.2-2280 NVME Solid State Drive ($99.99 @ Newegg)
Video Card: Gigabyte GeForce GTX 1660 Super 6 GB OC Video Card ($239.99 @ SuperBiiz)
Case: Silverstone SG13 Mini ITX Tower Case ($57.99 @ B&H)
Power Supply: EVGA SuperNOVA GM 550 W 80+ Gold Certified Fully Modular SFX Power Supply ($106.98 @ Amazon)
Case Fan: Noctua NF-P12 redux-1700 PWM 70.75 CFM 120 mm Fan ($13.90 @ Amazon)
Total: $979.80
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2019-12-26 19:17 EST-0500
