Let's see..
1 Power cable for the computer
1 Power cable for the monitor
1 Cable connecting the monitor to the PC
1 Power cable for the speakers
2 Speaker wires, one connecting them to the PC, the other to connect to the other speaker
1 USB cable for the Webcam
1 USB cable for the microphone
So far we're up to 8 wires.
My iMac setup? 1 Cable, the power cable.
That's your setup. I have four externals, speakers, iPhone dock, keyboard and USB hub connected. All those HDs I could have internally in PC, saving 8 wires (all are AC powered). For PC you can add stuff internally. For iMac, you do it via USB or FW800. So, I have at least 15 cables. Not very "cable-free"
Office is graphic / web development. No video editing or anything like that and storage isn't really an issue as the fileserver deals with all that.
Like I say, I am perfectly happy with the 2.66GHz MacPro (Dual Xeon) so if the iMac is AS good as that then I would be happy.
C2D would be fine but as your Mac Pro is dual Xeon (2x dual core Xeon i.e. quad core), the iMac would not be as fast. i5 iMac will be faster and as I said, take a look at refurbs, they get you a lot better deals. i5 will future-proof your purchase and for 300$, it really is worth it