RMS is root mean square... the example quoted above is not correct.
The connection is 1 Mbits and the download will be around 103 KB/sec ... which is equal to 103 X 1024 bits !
Root mean square is the mean average of a normal sine wave, usually u would multiple the amplitude of the wave with 0.707 to get the RMS value. ( that would yield the average DC component of an AC wave form).
what that means is, if u see the speaker's rating as 400W dont be deceived by that, always dig deeper in the documents and look up some more factors such as
RMS value
Impedence distribution
Frequency response range curve.
Best of Luck