lol funny how i mentioned the P180 and that happens to be the case you own.
Richard its far from over engineered. It has been considered one of the finest examples of affordable (if several hundred dollars can be called that ) near silent cases on the market.
Personally i wouldn't go ducting a P180 its chambered design keeps many of the hotest componets away from each other (the PSU and disk drives are seperated away from the CPU and have their own ventalation path). I would however invest in a better than stock
CPU cooler as well as some cable management (round cables are nice but proper management of flat cables can make them disapear). cleaning up the cables should give you better less turbulant airflow and offer better circulation. I would also turn the rear fans
to medium and turn up the front fans. This should create possitive pressure in the case and help keep out dust (air will escape from watever cracks it can find to balance the pressure). Also replace the missing brackets from the case they are letting cool
air out without cooling anything.