Thanks.Your speakers are efficient. You don't need amps to help them unless you are sitting a long ways from them and running them full range. And even then it is debatable.
You could get a cheap amp or two for the ATMOS speakers and be good.
I too got hoodwinked not once, not twice, but three times about external amplification -- and the third time, ponied up for a Mark Levinson design amp thinking surely an amp that costs as much as the rest of the system would be what people are talking about.
Nope. The only time it made a difference was with speakers that had sensitivity around 80. Then it helped.
Outlaw makes a 5 channel amp at 120watts per channel for for $749 MSRP plus $65 shipping that could do the 4 overheads. That makes the MRX-740 with amp almost the same price as the MRX-1140 and at that point I would just stay with the single-box solution of the MRX-1140 based off of your statements.