Here's the list I put together. I assumed your 1.5K budget included the parts you already have, so I worked on adding other parts from there.
For the CPU, the AMD Ryzen 7700X is a great mid tier chip for gaming and CPU intensive tasks. If you prefer Intel over AMD, you can swap it out for something like the
13600K at a similar price. I didn't want to go that route, however, because while the Intel chip has more cores on paper, more than half of them are low performance efficiency cores. For rendering and other CPU intensive tasks, the AMD's eight performance cores will beat Intel's six performance cores. If your budget did not include the parts you were gifted, you could swap this out for the
Ryzen 7900X, which will give you twelve cores instead of eight, which will also work better with the large amount of memory in the system. The 7800X3D, and other 3D variants are gaming oriented, so I would stick with the X series instead. 3D models are also more expensive.
You don't need a fancy and expensive water cooler to get great performance out of your chip. The Thermalright Peerless Assassin 120 is an amazing air cooler, especially given the price. If you have the extra cash, you could step it up to the
Noctua NH-D15, which is pretty much top of the line. This cooler will beat most water coolers. If you prefer water coolers,
Cooler Master and
Corsiar make great units, but I prefer air because of their longevity and reliability.
The motherboard is a solid option with plenty of features and IO. Again, if your current parts are not included in the budget you could step the motherboard up to an X670E board, which will give you the most flexibility over the B650 board I have on the list. Something like the
MSI MAG X670E Tomahawk would be a great pick.
Because I chose a Ryzen system, you will need to prioritize low latency over raw speed in your RAM. Ryzen CPU's will be heavily kneecapped on RAM with high latency. I went with a kit of Trident Z Neo 6000 CL30. This kit is pretty much as good as it gets for Ryzen systems, because it has low CAS latency of 30. This will work perfect.
For storage, you might want to grab a hard drive or additional SSD for extra programs, games, and content you might store on the machine. The
Seagate Barracuda 2TB is a great hard drive for the price, and will serve you well for mass storage. If you want something faster, the
Samsung 990 NVME SSD will suit your needs.
The case is really personal preference. I went with the Corsair 4000D Airflow for its professional design and emphasis on cooling. If you want something sleeker, you could pick up the Corsair
5000D or
5000X depending on your choice of tempered glass or mesh. There's tons of great case options out there if these aren't to your liking. Hope this was comprehensive and helpful, take care.