I have a MSI B550 Gaming Plus AMD board and can't decide what processor to buy or what would be best to use in my setup.
It depends on what you're using the PC for. If it's primarily gaming, I'd suggest Ryzen 7 5800X3D. It has 8C/16T, 3.4GHz - 4.5GHz, 96 MB L3 cache, and is the fastest CPU for gaming in its generation.
What do you do?
What is your budget?
What kind of cooling do you have/are going to use?
What power supply are you running/going to run?
going to use it to stream and play games. budget doesnt matter. cooling is a cooler master hyper 212 RGB black edition. power supply is a thermaltake smart 750W
Do you know exact model of your Thermaltake Smart PSU? .. or what it's rated? ..ie .. Bronze, Gold .. etc. You might want to invest in a better PSU .. even not knowing what GPU you run.
IF budget is no issue .. it'd be between the 5800X3D (fastest gaming) and the 5950x (might be better for streaming? ..and still fast at games)
With either CPU though .. I'm not quite sure if your current cooler would be up to the task .. perhaps someone a bit more knowledgeable about coolers will chime in and correct me if I'm wrong.
I ran my Noctua NH-D15 on the 3700x, 3800xt, 5600x, 5800x, 5900x and now my 7950x and it's performed fantastically on everything it's touched.
The Deepcool AK620 is an affordable alternative that rivals the NH-D15 in some tests
https://www.youtube.com/watch?v=UGM6FcLDckk
Cooler Master Hyper 212
https://www.youtube.com/watch?v=G38vEEGbkWU
While others already gave excellent inputs, I'm gonna focus technical aspects only.
The B550 Gaming is an low mid tier board that is pretty much compatible with all CPU's from 3000 and 5000 lineup.
However!
The VRM configuration of this board leaves much to be desired so I would keep Ryzen 9 chips away from this board.
Luckily, the 5800X3D doesn't need all that power and gaming wise is very up to date.
So its up to your wallet, GPU combo and Cooler.
Good Building!
I agree my old MSI MPG X570 Gaming Edge Wifi had terrible VRM cooling. Sticking with a lower power 8 core option kept it functional, but I wouldn't push too far past that.
I would look at reviews of people using that board to make sure the VRM is sufficient for the more power hungry 5900X and 5950X.