Bandwidth speed won't usually be the bottleneck because from my experience the downloads are done in bursts of a few megabits/second, and my node has a 1Gbps line.
Server processors such as Intel Xeons are usually good for sustained CPU activity but when running an intense single-threaded task like syncing
I'd say "it depends": I've seen my bandwidth maxed out during the first part of syncing, and I've seen my CPU-cores maxed out later on. I'm pretty sure Bitcoin Core does multithreading. If you fixed one bottleneck, something else becomes the new bottleneck.
My node has 16GB of RAM although I have almost never seen Core use more than 2GB at once.
It won't use it on it's own, unless you manuall increase dbcache.