So I'm currently running 16gb of Gigabyte Aorus ram at 3200Mhz, the Samsung B-die kit and have some money to burn... will I see much of a performance difference in going to a higher speed on a 9900k? I'll be looking at going to 32gb so I've got all my slots populated if I go for it while prices are low...
Which kits are recommended?
I used a Corsair Dominator PC3200 32GB (2 x 16GB) kit in my 9900K build. Been very happy with it. I run a lot of VMs for development work, so needed the capacity. In Aida64, it's about 50GB/s speed; I'd imagine yours is similar.
Unless you need the extra ram
capacity, I'd say just stick with what you have; any slight improvement in
latency is unlikely to be noticeable in the real-world (and the 9900K isn't anywhere near as sensitive to memory speed as Ryzen.)
Save you pennies for a better graphics card (etc.) in the future.