That's a great looking space - plenty of potential!
You've mentioned this would be used for movies and gaming then you said the kit would be put at the front. You may want to re-think this as all the lights and readouts would detract from your 'home cinema' experience. Your room is quite wide, you could easily put the kit towards the back, which takes me to my next point:
Your room is quite wide. In fact, almost square - I've read a few times that square rooms are often to be avoided for acoustical reasons. Personally, I would make a small storage/kit rack space on the left wall (door wall) which would narrow your room down by 2-3 feet. Alternatively, with all that space on the sides you may find that building double stud walls would be a wise move. When built with the proper decoupling, they provide better sound proofing than staggered stud walls.
You said you've done plenty of reading on this site, but a good long look at the articles on http://www.soundproofingcompany.com
before you start on any construction will pay dividends. You'll kick yourself if when it's done you have to keep the volume down so not to wake the kids/wife/neighbours.
At this early stage, don't worry too much about the equipment you're going to use (unless you already have it). Building the room properly takes time during which A/V kit either comes down in price or is replaced by superior alternatives.
Are you going for an acoustically transparent screen or having speakers in front? Personally, I prefer the AT screen - but you may feel that loosing 1-2 feet in perceived room length may make it feel a little too cramped.
Always remember the following:
There are plenty of people on this forum that have come across and resolved issues YOU WILL RUN INTO. Ask advice here - the worst that would happen is no replies.
Take your time. The room itself is the most important part of your home theater - equipment can be moved or replaced but you don't want to look back on it with the feeling you should have built the walls differently.
Take plenty of pictures. We need to see what's going on! Plus, more pictures = more feedback = often more advice when you get stuck.
On a completely different subject I read an interview with Tim Roth a long time ago. He was saying how he was tired of people asking him what was in the case. So, what was the next question?
"So, what was in the case"
"A light and a battery"