Svenna, I have read your posts and am wondering why you have an obsession with high network speed.
If you are looking for pure speed then you will need to shell out big money to change your network to fibre, your computers to 6 core processors with SSDs and fibre NICs then any NAS you get will also require a high speed processor and SSDs as well as fibre NIC.
If, on the other hand, you have an ordinary network, like most people, then you need to look at all the factors that can give apparent slowness on that network. Things like routers which are not switches and add overhead to anything that moves through them. Then there is cabling which can pick up noise if improperly sited and so slow packets down. Finally there are the computers themselves, most of the built in NICs are not the highest quality, unless you are running a server, and can vary considerably on same spec motherboards - in face we have one here that only manages half the speed of an identical MB.
The critical thing with any network is 'will it prevent you working because it is slow', if the answer is no then the network is doing its job. If the answer is yes then you need to find the bottle neck and fix it.