I've been wanting to build a Ryzen 9 3000 series computer. Best Buy had a deal on the 3900X and SN750 500GB NVMe drive for $450. I pulled the trigger and bought it. Picked up the Gigabyte Aorus Master motherboard. Went with the NZXT 510 case. I wanted a dual 140mm radiator but many have shared difficulties of fitting it in this case. Went with dual 120mm instead. But after getting more familiar with the case, there's a removable piece to mount the radiator on that could make fitting the dual 140mm radiator easier than shared by others.
The ram I went with is 3600MHz and CAS 18. I won't be playing much games and if I do, it's mostly older titles. This machine is mainly for development and running VMs.
I ran Handbrake and pegged all 24 threads. With the cooler, it ran 77*C. I'm using an older video card from a previous build. Waiting for sales on nVidia 2000 series super cards to go on sale and probably swap in the future. I wanted to use NZXT coolers but didn't find any that says it's compatible with AM4 right out of the box. So I chose Corsair.
I really like the build. The price is great. The biggest surprise for me is how great the NZXT 510 case is. But if I were to build again, I would choose a more featured case. The motherboard has more functionality that I can't use because of the mid-size footprint of the case. If I would've used a lesser feature motherboard, the case would match. But the case is really great for $70 and I would buy another for a lesser functional computer.
I used older hard drives to build a RAID5 for storage.
Overall, the system is running great. The build experience was also great specially with the NZXT case.