Alex,
I am sorry to tell you that the 701s do NOT have "pretty good bass for movies". The booming you hear is an exaggeration from about 100Hz to 200Hz to trick you into thinking you are hearing the "real bottom end". Trust me when I tell you that you are missing a tremendous amount of the audio spectrum and an incredible visceral experience without a sub.
The M80s have more accurate bass than the 701s. If you were to do an A/B test, you might believe that the 701s have better bass. But the 701s have bloated bass like I described above. Even with the M80s, you need a sub, period.
The 701s are a complete embarassment next to the M80s.
