You can install a total of seven fans in the P280 - all 120mm
Two in the top
One in the back
Two behind the door
Two behind the drive cage (tool-less)
So you have a few options - If you want to use the three fans that it ships with but are concerned about noise, there's a pretty good option to install the fans behind the drive cages instead of in the top.
i'm not sure that putting 2 behind the drive cages would do much if there are already 2 behind the door. with just ones behind the cage, it'd certainly be more quiet. does it really draw much air in or does it mostly recycle what's in the case?
me, i'd zip tie one between the graphics card and power supply to exhaust out through the expansion holes. should be much more quiet than those terrible blower style fans. then i'd have 2 120 mm exhausts out the back.
i might use one on top for an intake fan. since now there's some room up there. with the p180 and p183 that fan would practically touch a tower cooler.
antec used to include a vent cover with an HTPC case and sold it as a spare part per this spcr thread:
http://www.silentpcreview.com/forums/viewtopic.php?t=58675
why isn't there an option to hinge the door on the other side? i'm right handed. i prefer the computer to sit on my right. so the door opens the wrong way for me. this has been a minor issue with every antec case i've owned.