Ryzen 5 5600x and a 3070/3080. I'm telling you right now, you are not going to be able to get a 3070 or a 3080 next month. People have been attempting to buy these for months now with no luck. You gotta get really lucky when they restock or you gotta bot one. ZOTAC restocks their 3070s a lot but they aren't the ideal 3070 to get. A 3070 is a 3070 so if you want to get one, try for it. I'm in a Discord that tracks 3070/3080 drops and it pings you when a retailer restocks. If you're building or upgrading these days you are going to want to upgrade to a RTX Ampere card or the new AMD Big Navi cards. They're both extremely hard to get now because scalpers and bots are scooping up everything. You will end up paying a round $600-$700 on a RTX 3070 if you are desperate enough and can't nab one at retail. I've had a couple of offers so far for 3070s that I have turned down because I don't want to overpay too much for the card. I've been offered $600 that I absolutely regret not taking and $650 that I was more iffy on. I was also offered to buy a $560 MSRP card for $730 from some moron in the NVIDIA Discord. You just gotta get lucky... Browse /r/hardwareswap on Reddit if you want to buy one used or sealed. Like I said though, you'll be paying $600-$700 anywhere that is not retail.
Here's a document that will tell you everything you need to know on how to secure a 3xxx card:
https://docs.google.com/document/u/1/d/14M3rQQSWW4OPgnRkxbMr1hTEBEwPm3449KINbJJgGA8/mobilebasic
Good luck. I have been trying myself for a while.
What @deliriumsaid about watercooling is true. I thought about getting an AIO but my dear friend @vinylshowed me the be quiet! Dark Rock Pro 4. It is an absolute bitch to install but it's worth it. I get really good temps compared to the stock AMD cooler and it is fairly quiet. It is absolutely massive though so you might have to check if you have clearance for RAM or whatnot. oh, and find someone with tiny hands to help you install it.
I put this together for you.
PCPartPicker Part List
CPU: AMD Ryzen 5 5600X 3.7 GHz 6-Core Processor ($299.99)
CPU Cooler: be quiet! Dark Rock Pro 4 50.5 CFM CPU Cooler ($89.90 @ Amazon)
Motherboard: Asus ROG STRIX B550-F GAMING ATX AM4 Motherboard ($184.84 @ Amazon)
Memory: Corsair Vengeance LPX 32 GB (2 x 16 GB) DDR4-3200 CL16 Memory ($109.99 @ Best Buy)
Storage: Western Digital SN750 500 GB M.2-2280 NVME Solid State Drive ($62.99 @ Amazon)
Video Card: EVGA GeForce RTX 3070 8 GB XC3 ULTRA GAMING Video Card ($559.99)
Total: $1307.70
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2020-11-24 09:02 EST-0500
I put in the prices for the CPU and GPU manually because they are not in stock anywhere. It's going to be a pain to source either but it is completely worth it. No point in getting anything else if you aren't dying of desperation to get a new system. As for the case, get whatever you want lol. It's your preference and the design you like. I'm not going to shove a case down your throat. Keep your current storage and add that NVME I put in the list. I don't think I'm forgetting anything? You could look into getting another AMD Ryzen CPU. Those things are really great and you seriously can't go wrong with them. No point in getting an Intel CPU nowadays. You could also get a different motherboard. I'm not too knowledgeable on them but I picked that one based off of personal experience. Idk. Good luck, champ.
Adding this:
Ryzen 7 3700x is on sale right now for $279 at Best Buy. It is also a really good CPU and it is a nice alternative if you cannot find the 5600x. I recommend browsing /r/buildapcsales for some nice deals. Sometimes retailers make stupid errors and you can cop nice parts for stupid cheap prices. There are also times where there are just some really good sales that aren't marketed that well.
I'm finding a lot of really good deals on things right now like cases, storage, CPUs, etc. and it isn't even Black Friday yet. Right now and Black Friday would be the best time to buy parts if you can, @fantastic.