There's not a lot available on the 770 yet -- it's got 7 channels at 200W per channel (20Hz-20kHz@8 ohms, >0.07%THD, all channels driven according to the updated FAQ), it will be priced at $1799 with an unknown "family" discount available if you own or are buying some other Outlaw gear, and it reportedly weighs a lot. More information should be out in the next month -- it is scheduled to ship at about the same time as the 950. The 750 has 5 channels at 165W per channel, and has proven to be a very solid amp in the couple years that it's been on the market now. At $1099 before the $50 "family" discount (that's the discount if you also buy a 1050; I'd anticipate that it'd be similar if you get a 950 with it), it's a good value.
I guess that if you plan to set up 6.1 or 7.1 immediately, the 770/950 combination would be very effective. If you'd like to hang on to that extra $700 and don't need 200W per channel, the 750 is a very nice amp. Drawbacks to the 750 in that case: you'd need to add an amp for the center surround (which could push the total amp cost close to the cost of a 770, but would let you delay some of the cost if needed), or add a big two-channel amp for the mains (which would probably drive the total amp cost close to or higher than the 770).
As for speakers, you might check out the "Speakers" forum here -- lots of setups listed there. There are a number of "package" type speaker setups mentioned there, as well as some more robust options (which might be more to your liking if you are considering the 950/770 combo to drive them). I personally have been very pleased with my Paradigm Reference speakers (Studio/60's as mains, Studio/CC center, and Studio/ADP surrounds).
[This message has been edited by gonk (edited October 29, 2001).]