lso bear in mind that having 100s of MB does not make your WiFi any faster..
If it's an 802.11g router then the max is about 8MB/s - shared across all the connected devices.
802.11n and ac are much faster, but only if the router and device are both capable - older ones may not be.
We manage fine on 40MB between 5 of us , but we have two WiFi routers one of which is n speed.
If the device doesn't move it's best to wire it up to the network rather than use wireless as Ethernet supports 100MB minimum.
The general thrust of your post is correct, but please differentiate between B and b in network speeds! 1Byte = 8 bits, so your 40MB is 320mb! Network speeds are, conventionally, expressed in bps (bits per second). Originally in bits, then kilobits (Kbps), megabits (Mbps) and now gigabits (Gbps).
SD