Gigabit ethernet's maximum transfer is 128MBps. You are unlikely to see this speed in real life however. Obviously things only get worse if you use fast ethernet or wireless.
Average read benchmarks for a 2TB drive, say the Samsung F4 which is a green drive, come in around 100MBps. If you were to RAID these drives I'd expect to see an increased performance. How much will really be down to the raid controller.
So only in perfect network scenario will the network be able to keep up with the read speed.
My advice to you would to buy two 2TB HDDs from different manufacturers.