Yeah, the only reason I would choose the A-S301 is because Yamaha doesn't offer the 2/5/7 Ch amps like Marantz.
The A-S301 will work just fine for OCD people (like me) who must have the SAME brand for the electronics if possible.
If I owned Marantz, then I would add the 2Ch Marantz for the extra 2Ch.
But there's no way I'm adding a Marantz Amp to a Yamaha AVR.
So hopefully Yamaha will offer these 2/5/7 CH amps in the future.
But since they don't offer them currently, the only other small consumer (not Pro Amp) amp is the A-S301. Which will work just fine for the purpose of extra surround sound amp.