Very good point there ElectrO...investing THAT MUCH into a CPU doesn't really make much sense, assuming that the OP is playing at 1080p60. Theres almost NO performance gains to be had, assuming that the 8100 is the equivalent of the 7400...https://www.techspot.com/review/1463-ryzen-3-gaming/
As for max's build, is it REALLY that much better of a gaming build? You need to remember that by sacrificing the SSD, the OP would be limited to stagnant HDD speeds...gaming on an HDD is one of the worst blows to an experience imo. OP, I understand that you may like ATX boards for their aesthetic/expandability, but I must emphasize to you that THEY ARE NOT WORTH THE MONEY in this scenario. While it IS true that you'll have either upgrade your board/RAM layout if you want 16 GB, 8 GB should still be fine for gaming for quite a while. I would recommend following this build:
PCPartPicker part list:
https://au.pcpartpicker.com/list/G468ZR
Price breakdown by merchant: https://au.pcpartpicker.com/list/G468ZR/by_merchant/
CPU: AMD - Ryzen 3 1200 3.1GHz Quad-Core Processor ($139.00 @ Scorptec)
Motherboard: Asus - PRIME A320M-K Micro ATX AM4 Motherboard ($79.00 @ PCCaseGear)
Memory: Team - Vulcan 8GB (2 x 4GB) DDR4-3000 Memory ($133.00 @ Umart)
Storage: Kingston - A400 240GB 2.5" Solid State Drive ($69.00 @ Umart)
Video Card: Gigabyte - GeForce GTX 1060 3GB 3GB Windforce OC Video Card ($299.00 @ Shopping Express)
Case: Deepcool - TESSERACT SW ATX Mid Tower Case ($49.00 @ PCCaseGear)
Power Supply: Corsair - CXM (2015) 450W 80+ Bronze Certified Semi-Modular ATX Power Supply ($75.00 @ Shopping Express)
Total: $843.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-06-20 04:22 AEST+1000
Substituted the i3 for the 1200, although the i3 is undeniably good for gaming, if it's not above 60 FPS then the OP will be more GPU bound than CPU bound. Still retained that 3 GB 1060, definitely the right choice for higher-spec gaming:
https://www.youtube.com/watch?v=aNoltJNvpew
It would be better to go for the SSD first, since you wouldn't have to reinstall windows. Not to mention, you could EASILY find a spare HDD in let's say your old PC, ebay, etc. The SSD makes a HUGE difference in game loading times. All in all, I think this is your best option at this point.