Your computer components are geared more towards the back in a traditional computer case, where most of the hot spot reside, therefore it's wiser to have an intake fan in the front. The front where the fan is attach is usually lower and sits under other component so it won't have to worry about the heat that will be dispense if other hardwares were under it (heat rises).
The back fan as an exhaust because the back of your case where the fan is attach is usually higher than the front of the case (because the CD/DVD hard drive and floppy occupied those space already). The exhaust fan and the PSU will help suck out air together, that's why you should put the exhaust fan in the back.
They make great cooling products, I suggest you buy a fan controller as well. This is useful for controlling the speed of your fan when you're playing games and when you want it to just be quiet. Try finding one that will turn the fans off if you want complete silence.
Also, if you want to make your system quieter, try getting one of the zalman cpu cooler. They usually come with a fan controller for the CPU fan. And don't forget about your PSU fans, some PSU you can change the fan and some you can't. Just get a new, quieter, good brand name PSU.
Have you ever thought about doing liquid cooling?