Are they that loud? Mine aren't. You need the intake as well as the rear exhaust. The top exhaust is less important, but the 200mm fans are very quiet. Also, you say the 212+ will cool your CPU. How will it cool it when it cannot get fresh air nor exhaust the hot air out from the heatsinks?
Even with the Hyper 212+ if you do not have sufficient intake and exhaust you will just be pushing the same hot air in the case with no place for it to go. That said you might be able to get away with just the front intake and rear/top exhaust. Monitor your temps including the mainboard and cpu and see what you can get away with.