For a 9800X3D, 6000MHz CL30 is a great sweet spot for performance and price. A 32GB or 64GB kit of that spec should work well. If you're aiming higher, 6400MHz CL32 kits (like the Corsair Dominator Titanium RGB) offer excellent performance, but ensure your motherboard supports it.

I will choose DDR5 6000 CL30.

Just saw this thread and realized nobody asked—what motherboard are you actually looking at, and is this purely for gaming or are you doing some heavy editing too? Honestly, since the 9800X3D has that massive 3D V-Cache, it’s not as picky about raw frequency as the non-X3D chips, but the timings are still super important for those 1% low frame rates during intense scenes. If you want a kit that just works with zero headache, I’ve been running the G.Skill Trident Z5 Neo RGB 6000MT/s CL30 on a few builds lately and the EXPO profiles are basically flawless for AM5 stability. If you're feeling adventurous and wanna try pushing for 6400MT/s to see if your FCLK can handle it, the TeamGroup T-Force Delta RGB DDR5 32GB 6400MHz is a solid bet since they usually use Hynix A-die which is way better for stability when you’re manual overclocking. Just whatever you do, dont try to run four sticks at those speeds because the memory controller on Ryzen will just cry and you'll end up stuck at like 3600 or something crazy slow, so definitely stick to a 2-stick kit for sure.

Re: "Any decent DDR5-6000 kit from a reputable brand..." - honestly its kinda disappointing how many kits claim stability but then throw errors once the case gets warm. Used to trust almost any big name but lately there have been issues with some generic 6000 kits not holding their profiles properly under load. If you want something that actually performs without the headache tho, the G.Skill Flare X5 Series 32GB DDR5-6000 CL30 is a solid bet since its low profile and built for AMD specifically. Another one that flies under the radar but works great for performance is the ADATA XPG Lancer Blade 6000MHz CL30. It uses Hynix chips which are basically the gold standard for those tight timings you need to keep the 9800X3D feeding fast. Just wouldnt push it to 6400 unless you really know your way around the BIOS. Sticking to 6000 is safer and the performance diff is basically tiny anyway... lmk if you run into any boot issues during setup.

Any decent DDR5-6000 kit from a reputable brand will work fine. I'm using Crucial's 32GB kit (6000MT/s) with my 9800X3D and haven't had any issues. Just make sure your motherboard is on the RAM's QVL list or vice versa for best compatibility. 32GB is the sweet spot for gaming and general use these days.

The Sweet spot for 9800X3D is DDR5 6000 CL 30.  https://www.amazon.com/s?k=DDR5+6000+CL+30&------123456890?7649-20

Kingston Fury Beast at 6000MT/s CL30 and getting excellent results.