Has Anyone Compared the 2 McIntosh Integrateds?

Pardales, as to your tone control question, yes, they are "deafeated" when they are set in the middle. Obviously the signal must run to the tone controls, but the signal is not altered by the tone controls when set at the 12 o'clock position.

According to my manual for the MA6500, power output per channel is 250 watts at 2 ohms, 200 watts at 4 ohms, and 120 watts at 8 ohms. The question of ability to drive large Magnaplanars can only be answered based on the size of your room and the volume level of listening. I would expect either amp to drive the speaker in most reasonably sized installations. The 6900 may run cooler with lower impedence speakers, but if the 6500 was not enough power for the room, I'd expect that neither would the 6900. I would expect a larger external amp would be more appropriate. A switch on the back of the 6500 allows connection of an external amp instead of, or in addition to, the built in amp.
Good deals on the MA6500 via Audiogon classifieds and ebay have appeared. I bought mine in new condition via Audiogon for $2250. One sold for less on ebay a few weeks ago. Being so new, I have not seen MA6900s available on the resale market.

Not only are tone controls defeated at the center position, but "All tone control circuit elements are removed from the signal path when the controls are in the center or flat position." ...MA6500 Manual.

These are all valuable technical details that are helping me undestand the differences, but has anyone compared the sound of the two amps? I prefer the MA6900, but again, that $1500... I would appreciate other impressions.

I really do appreciate the specific input from you all. Moniker: I have not heard these specific units yet (though I have heard other Mac stuff). I am looking for a dealer that actually has either of them to be honest. I have one dealer close by but they only carry the Mac seperates. I'll keep checking this thread for more information and if I get any more I will re-post here or email you directly. I am beginning to like the idea of going with the 6500 and spending the extra money on new music. I'll be keeping my eyes open for a slightly used and cared for one. Thanks again to everyone!