One thing to consider if you are going to put your equipment in the closet is ventilation. An awful lot of stored heat can build up in a closet over a short time, so there needs to be an outlet, and maybe even a fan to help draw the hot air from the top - on one install a while back I put in a standard rectangular register right above the closet door, left open to the inside of the closet, and installed a dual rack mount fan unit on the inside portion of the register, and above the equipment to help pull air up and out.
From the outside, it looks no more out of the ordinary than any of your other typical A/C vents, and can be painted to match whatever your wall colors are.
Depending on your attic and truss configuration, hopefully it wouldn't be too difficult a task for you to pull the required cables up the wall and over to the closet via the attic, but it will make for a very clean, professional appearance of your system in the end.
I would suggest also, terminating with wall plates at the TV/Speaker end, and running the whole bundle together from your attic penetration into the closet - make as small a hole as possible and if you have it use some sort of cable cover (snake skin or equivalent), which can be found at Parts Express.
Also, all the ventilation you put in will likely not do as much good unless you have an equipment rack that can breathe - a lot of people have used standard steel wire bread racks, unless you have a lot of money to spend on a professional A/V equipment rack that has all the necessary ventilation ports and louvers built into it to allow for proper air flow.