Each component can help and hinder the network and you'll discover how much when you make the changes. I do try to estimate which changes will, generally speaking, have the greatest impact. Network Adapter A network adapter is a device that physically connects your Mac to your network, converting the network signals into data for the CPU and vice versa. Ethernet's three speeds can be deceptive, since they imply you can increase your network speed tenfold just by purchasing a faster network adapter. Sadly, this is not the case.
Most Ethernet networks use a hub or switch as the central connection point.
The hub manages the network traffic, moving the data where it needs to go. You need a hub that supports the given speed rating to use it on your network. People often ask me whether to purchase a hub or switch for their network, since hubs are cheaper but switches usually advertise themselves as more efficient. If you move a bunch of data around the network, you may notice a speed difference between a 100 Mb hub and a 100 Mb switch, but you also may not. Your hub must support your highest network speed to make use of it, but otherwise the model and make should make relatively little difference in speed.