Finally, there's no functional difference between killing/knocking out/avoiding NPCs.Each upgrade you purchase will also stack with the previous ones, even though the text doesn't make this very clear. You can see through walls with them and even tag people while doing that.
Completing optional missions will unlock the highest tier suit upgrades for purchase. They'll be about 200k a pop, but the rifle and pistol with inherent silencers are absolute beasts and if upgraded can punch right through armour in a couple of shots. If you're really desperate you can replay earlier missions and just grind money out that way (there's no point reduction for replaying levels), but it's probably best not to do that unless you're going to try a different playstyle shit might get old if you're following a routine.
