What you paying to build it yourself? this deal might be better. only comes with a 260watt PSU but it does have a 16x slot. 4700g gives you 4 more CPU cores and about 5-10% more GPU performance
570$ 4700g
https://slickdeals.net/f/14908247-i...-7-4700g-16-gb-ddr4-3200mhz-567?src=catpagev2
AMD® Ryzen™ 7 4700G Processor (3.60 GHz, up to 4.40 GHz Max Boost, 8 Cores, 16 Threads, 8 MB Cache)
16 GB DDR4 3200MHz (2 x 8 GB)
1 TB 7200 RPM HDD + 256 GB PCIe SSD