CN-235 certainly doesn't have a "go quiet" feature. Its a stol hi wing which means that it makes a racket under load when taking off
Its a light transport as well, and as pointed out is originally a Spanish design from CASA.
Australia was looking at 235's as part of our Caribou replacement prog, we looked at the original Spanish product plus an Indonesian licensed built version.
In the end we killed the entire project off. As other more pressing requirements needed attending to (like C130J's)
The Y-8 hasn't been updated since 1987 and is far less capable than a Herc. (eg you can't carry vehicles in it) Its a great air ambulance, air taxi, but useless for transporting armed forces and their requisite motorised gear. No ramp for rear loading. It's like a 4 engined Fokker Friendship.
as for the Mriya AN-225, no more are being made and the ones that do exist are making an absolute fortune for their operators by long leasing them to the UN etc... Australia leased one for a while. Nice heavy lifters, but I wouldn't want to buy one due to the typical russian problem with reliability (eg one got stuck in Afghanistan for about 2 weeks as they couldn't find spare parts for it)