Here's a pic of a setup that I'm considering purchasing:

Can anyone help me identify a few things?
Lower right corner - what is plugged into the I/O board? Obviously, the USB cable, but what are the other wired connections?
There's a small yellow cable that connects to the bottom left corner, but I can't tell where it goes... Same with the connector just to the left of that.
Left Side What is above the audio amp?
Also, what is all of that stuff below the audio amp? I've not seen that stuff before.
In terms of being able to connect this to a Net City cabinet - is it all even necessary?
Which of these things would I definitely not need with the NC cab, if any?
Finally, if I did plug this into a NC cabinet, what would I plug everything into?
There are some great references on this site about connecting the setup, but I'm having trouble finding good pics & info on connecting this to a non-Jamma cabinet like the Net City.
Thanks to everyone for your help.
P.S. - In everyone's honest opinion, is this setup worth $500, or is that too much?
Thanks again,
Steve