UserBenchmark gives a 48% preference to the i3-6100 over the FX-6300. Good call on that.
Still, as this build is just slightly over budget, I'd consider stepping down the CPU just slightly to the Pentium G4500 to save some money. The i3-6100 scores 8-15% above the G4400/G4500/G4520, but all three of these G-series Pentiums handily defeat the FX-6300 in UserBenchmark scores. (G4400 vs FX-6300, G4500, G4520)
The PSU seems like overkill; 750 watts aren't needed on a build like this, it doesn't even crack 400W power draw. Yeah it leaves room for expansion, but maybe a little bit could be saved on a lower-power PSU and get under the $550 hard limit.
The case doesn't have any front-panel USB 3.0 ports, so there might be some concerns there. There may also be difficulty fitting in a longer graphics card without blocking drive bays.
The system as listed doesn't have an optical drive, which may make installing Windows 8 from DVD a bit challenging, especially if access to another computer to make a bootable USB stick isn't readily available.
With all of that in mind...
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Pentium G4500 3.5GHz Dual-Core Processor | $83.86 @ NCIX US |
| Motherboard | Gigabyte GA-H110M-A Micro ATX LGA1151 Motherboard | $49.99 @ Micro Center |
| Memory | Crucial 8GB (1 x 8GB) DDR4-2133 Memory | $28.99 @ Newegg |
| Storage | Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive | $45.89 @ OutletPC |
| Video Card | Sapphire Radeon R9 380 4GB NITRO Dual-X OC Video Card | $174.99 @ Newegg |
| Case | Rosewill SRM-01 MicroATX Mini Tower Case | $21.99 @ Newegg |
| Power Supply | EVGA 500W 80+ Certified ATX Power Supply | $34.99 @ Amazon |
| Optical Drive | LG GH24NSC0B DVD/CD Writer | $13.99 @ Newegg |
| Operating System | Microsoft Windows 8.1 OEM (64-bit) | $89.99 @ NCIX US |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total | $544.68 | |
| Generated by PCPartPicker 2016-03-27 18:47 EDT-0400 |