Perhaps AMD is concerned that their products fall into the same hole that Intel had, the 9950x and 9950x3d all have a new limit called HTFmax, which means that even though they don't reach the max temperature, the frequency will still go down. Only when the CPU is below 55 degrees can I saw it running at 5.5G+, and the frequency won't go higher than 5.35G when it's 71 degrees.
I tested it with a low-end 360 AIO(45USD), a high-end air cooler(45USD) and a budget air cooler(15USD), none of them can significantly press the temperature down to avoid the CPU from being limited by the HTFmax.
So, I'll recommend a air cooler whose performance is similar to Coolermaster Hyper612. Adding more budget to the cooler won't significantly improve the performance until you use a distributed water cooler which is connected to a compressor (is it so called in English? I mean, not an AIO but a manually built water cooling system), but it's very expensive and not easy to maintain.
Some extra info about AIO:
I bought this AIO because a famous tester tested all famous AIO and asked the manufacturer about their products, and only Deepcool and Valkyrie send an engineer instead of a manager for answering. The engineer from Deepcool said that Deepcool focus on stability instead of extreme performance, thus installed a decompression valve on the AIO to avoid leaking. Deepcool had got great loss 10 years ago due to its high performance "captain AIO" 's frequent leaking, after that, it made the decision to focus on stability.
The manufacturer that choose an opposite way is Valkyrie, it tends to choose extreme performance instead of stability, but it provide great warranty. I haven't tested a Valkyrie AIO on 9950x3d, but I think the R23 score will not get great advance unless I bought a $200 v360AMG.