I want to be able to play Half-Like: Alyx at max prettiness with an Index and I've got the money to burn.
Hit me up with recommendations and advice and all that good stuff.
If I had money to burn, I'd be considering the following:
CPU:
If you want Intel: Intel i9-9900K or i9-9900KS. 8 Cores/16 Threads. Looking at PC Part Picker, you're looking at a starting price of around $480 and up.
If you want AMD: Ryzen 9 3950X. 16 Cores/32 Threads. When in stock, costs $749.
You'll need to buy a cooler for either CPU. AMD officially recommends an AIO liquid cooler for the 3950X.
MB:
A Z390 motherboard if going Intel.
An X570 motherboard if going AMD.
You need to figure out what CPU you're getting first, as well as what features you want. For example: do you want to overclock/do it well? Do you need Wi-Fi? What about the form factor? Do aesthetics matter to you? Etc. MB prices vary, but first you need to identify what you want out of your motherboard.
RAM:
16GB or 32GB of DDR4-3600 CL16 RAM.
16GB should be fine for normal gaming. Since Half-Life: Alyx has a requirement of 12GB, 32GB might be worth considering as RAM prices have gone down and also if you plan to do more than game (game streaming, content creation, video editing, etc.). Can't say if 32GB of DDR4 RAM (or any PC tech) is future proof as there's always something better around the corner.
For top of the line/overclocking/better timings, you'll want a kit that features Samsung B-Die RAM. Micron E-Die is also good, but not as good as Samsung in that regard. You'll want to pick out a CPU and MB though, and see what RAM is on the vendor's QVL. You will see diminishing returns past DDR4-3600 (actually DDR4-3733) on Ryzen, though.
Currently, there are 16GB Micron E-Die-based RAM kits on Newegg for around $75.
GPU:
NVIDIA RTX 2080 Ti
The best gaming GPU you can buy right now, outside of a Titan RTX, which is more than double the price and also intended for enterprise. 2080 Ti pricing starts at ~$1000.
VR is more demanding than normal gaming due to rendering. If you want the best for this, the RTX 2080 Ti is currently it.
SSD:
You're going to want a 1 or 2TB M.2 NVMe drive.
Samsung SSDs are the best in this category with their 970 Evo line, but you will pay Samsung tax for that quality. That being said, there are good 1TB M.2 SSDs can be had for ~$100-120 on sale, especially now during the holiday sales season. There was an Amazon lightning deal yesterday for one (~$80) that sold out in like 10-15 minutes.
PSU:
If you go with the high-end components listed above, your existing 650W PSU might not cut it if you plan on any overclocking. For that extra headroom, you'll want a high quality 750W PSU. Corsair has the HXi and HX Platinum series which start at ~$150. For a little less but still good, their RMx Gold series starts at ~$120. Given the components you intend to get, cheaping out on a PSU is generally not recommended.
Case:
This will vary on what form factor you want, aesthetics, tempered glass, RGB, etc. Buy whatever appeals to you, but be sure to seek out reviews for the case's thermal performance out of the box.