Two things I must input about the above. Those are not bad tools but I can think of two big drawbacks.
1. I don't recommend buying a rotary tool that uses rechargeable batteries - they are literally weak and the charge is depleted pretty quick. Not good for case modding uless you have lots of time or lots of cash for spare batteries. Get one with a plug.
2. I don't suggest buying a rotary tool that the rpms cannot be adjusted either. When cutting thru plastics you will need to be able to lower the rpms. 35,000 is really high for that. Get one with an rpm adjustment.
Good luck and happy modding, I got some pics in my sigs.