As to engines, I found my Holy Graal already: I use
Improved Engine Sounds mod by BillyBubble and it's perfect. It not only gives new, better sounds for engines, but also solves some other issues - the sound transition between compartments and outside is much better, closed/open hatches now influence the noise level better, it's just overall excellent mod. No other mod I checked has so good engine sounds.
Just install it after any other sound mods and it will overwrite the engine related sounds.