Yes both the M-Box and Emu card can be installed simultaneously. As far as wheter or not installing a PCI card is dangerous is concerned, I guess is determined by your technical abilities. Obviously installing Firewire is easy. Installing a PCI card is as easy as Opening the computer case, inserting it into the PCI Slot, tightening 1 screw, and closing the case back up (Be sure to read all instructions first, and follow directions in regards to static electricity). Then install drivers. Really easy. I think it is more of a question of convenience than risk. Firewire allows for you to simply unplug the soundcard from one computer and into another (Especially useful if you plan on working on more than one computer, especially if a laptop is involved). If this sound card will be primarily installed in one desktop machine, either one will work (But your more likely to get more features per dollar out of a PCI based setup).
