Tow minor problem I see:
1. Light/switch mounts. On a Dell, they have a harness from the case that is made to fit the motherboard. I highly doubt the motherboard is going to say where each connection is. So you will probably have to play around with it a bit to get the switches and lights working properly.
2. Power supply. A bigger case will mean longer power cords, and it is doubtful the power supply in the Dell has cords that are 1 inch longer than they need to be, so I would plan on purchasing a new power supply as well.