I did a whole bunch of testing when I bought my first B One, I am very impressed by what it can do. If you have a 1GB symmetrical connection, it won’t handle it. Best I did was about 600Mbit symmetrical or very close to gigabit in one direction. I did manage over 900Mbit with 2 USB network cards too and the best total router throughput (3 internet connections, 1 USB to 3 computers) was 1.4Gbit at about 60% CPU usage. Way higher than I ever managed through a Balance 305.
I did a bunch of testing with different USB adapters but I did test a few other scenarios I didn’t post and overall found it to be a very capable device.
That said, if you need faster, the new B310 has dual 2.5Gbit WAN and 4x10Gbit LAN and the new B580x is supposed to have more. No leaks on the total throughput of the devices but they should be out by end of year.