Did you miss the part about:
-Wall of 80mm fans
-No justifiable setup
-80mm...
-Alienware
-Should of bought a new case, heatsinks, or both
I'm a little worried about you.
Yes definitely cut a few holes behind the motherboard, you'll also have to fish the front panel wires through the HDD bay and 5.25" bay which is a daunting task. Good luck and yes it is worth it :)