No, You Cannot Bi-Amp

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I wouldn't know a crossover from a crossbow. I want to get myself a pair of the 20.7 and I'm glad to know that the new design allows you to power the speaker with one amp without having to worry about whether it would sound better with two amps. I'll just make sure the my amps have plenty of muscle at 4 ohms in order to dominate the speaker.
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01-18-12: Elizabeth
In my mind biamping is a 'teenage' phenomenon.
If one is good, two MUST be better.
Yeah a few folks are able, with effort to make it work for themselves.
In general it is a waste of time, if as much effort was made to have one amp work well.
The worst side of it is all the folks who know nothing about it wanting to do it as if it is some easy magic panacea.. Gee I could biamp,,Cool!.... NOT.

OMG, there you are again spewing BS on a topic that you have no technical knowledge of (& once again you have to be reminded of the same). Like in many other similar posts of yours,I have earnestly requested you to not write garbage on a topic esp. if it calls for a technical explanation. This only continues to spread "old wives tales" on the subject matter which disallows this audio community from getting more informed. This request is being made once again....

Mitch4t,
here is a nice (& lengthy) article on Series vs. Parallel Crossovers.
http://sound.westhost.com/parallel-series.htm
You can see (immediately) that the series crossover has only 1 input hence bi-amping is not possible (the author states this himself as well). From this article & the technical measurements it's quite clear to see that (iffffff) the series & parallel x-overs are done right, they are nearly identical (& the author even states this in the concl para) in their performance so this hyperbole of the Maggie 20.7 x-over being much better than its prev revisions due to it being a series x-over is pure BS! The 20.7 xover might/must be better (I've not heard the 20.7 myself) maybe because Magnepan decided to spend the time & patience to do it right after all these years?? (speculation on my part but who knows the exact reason for it being better - certainly not due to it being a series xover...)

Biamping made sense when amplifiers exhibited lots of IM distortion and a high powered amp was 60 watts. Not the case today.

True biamping means that you use a line level crossover. Such a crossover is usually superior to a passive crossover, and much less costly if the passive uses high quality parts. IMHO, the crossover is the chief advantage.

Subwoofers are almost always biamped.

So folks who use monitors with powered subs are idiot children? Its the exact same thing as those who say choose to power woofers with a beefy SS amp and power top end with warmer tube sound (for example).

Bombaywalla, I agree with your take (I think). It's not so much about the theoretical considerations as it is the execution. Maggies have perpetually been subjected (with good reason) to modifications of their crossovers. Peter Gunn made a pretty nice business out of his crossover mods. Others have gone to the trouble to use external active crossovers, and swear that takes the Maggies to a whole new level. If the new crossovers are better than the old stock ones, it is likely due to better parts and better execution, rather than the inherent advantages of the series design. All I know is, the stock 3.7's sound a whole lot better to my ears than the stock 3.6's, which leads me to hope for a similar improvement in the 20.7's over the 20.1's. But the advice remains, go listen, let your ears be your guide.