Just a quick couple of thoughts.
You want some level of separation between electrical wires and network/audio/video cabling. You run the risk of interference if you put them too close. Best practices for network wiring states that if you have to run a network cable near an electrical cable, try to NOT run them parallel, and if they must cross, make it as a 90 degree angle to reduce the proximity. I don't know what would happen if you put your network terminations right next to all of the electrical going in/out of the breaker box.
Not saying that it won't work, but just to use a bit of caution and maybe research it a bit.
As for conduit, you have hit the age old problem of filling up the conduit with current wiring and not having room for new.
There are really only a couple of solutions. 1) run 2 conduits in parallel with each other. One for now, and one for expansion. 2) Reduce what you put into the conduit by taking things like the 12ga speaker wire and not putting it in the conduit. Speaker wire should be fairly safe if protected by a decent height off of the floor and placed far enough back to prevent a nail/screw from hitting it (or use stud cable protector plates). That should open up some space inside the conduit.
Keep in mind that the conduit also needs very gentle curves in order to get any future cabling through it and a lot more space than you think you may need.
Otherwise, this is going to be fun to follow the progress.
