Make sure you get a box that is fit to the dimensions specified by the sub manufacturer. If you can spare the cash, get it custom built for better results. It'll run you about $100-$150 CDN for a custom and maybe $60-100 for pre-built. It's not much to upgrade, just have to find someone willing to build it for you.
Your amp is probably MTX's 6500D. That will out put 500 W RMS. It's a good amp. I'm running the older model of that, the MTX 500D which has the exact same specs except its older. I bought it second hand and it runs well. Doesn't get too hot.
Your sub is probably a 10/12" W3v2 which runs at 300 W RMS. Your amp will definitely run your sub fine. However, I'd suggest you ensure that you're getting a dual 2 ohm. This will run you at 4 ohms right now. Your amp will push 500W RMS at 4 ohms and so you should be covered. As well, if you decide to add another sub into the mix, that will drop your impedence to 2 ohms and your amp should put out somewhere between 775 and 1000 W RMS. Once again, you'll be safe.
If for some reason you can't buy a dual 2 ohm and you have to settle for a dual 4 ohm. You'll be running at 2 ohms right now. And later on when you want to upgrade to 2 subs, you'll either have to push your amp to 1 ohm (I don't suggest this). This will then void your warrantee and you run the risk of blowing it. I don't believe MTX's 6500D is 1 ohm stable. It may be, but once again it'll void your warrantee. DVC 2 ohms are kind of hard to come across in retail stores sometimes.
You should be able to get away with 8 gauge wiring. When I set everything up, I bought an 8 gauge wiring kit. I'm running 500 W RMS to my subs so you'll definitely be fine. Maybe if you intend to upgrade, get a 4 gauge installed now because the components in a 8 gauge kit and a 4 gauge kit are different. Get it right now rather than later?
Some people have said that it's cheaper to purchase parts from the kit seperately. I haven't confirmed it but I suspect that will probably be right. Do some research.
I don't know what your deck goes for retail, I don't even know much about that deck. Sorry, can't give any feed back on it. Just ensure that it's detachable and make sure you take it everywhere you go. I bought one with a motorized flip. I take it with me even though it "hides".
Have you checked the second hand market? I bought my deck from retail since I got it near cost price from a friend. The speakers were also bought from retail from that same person. However, when I invested in my low-end, I got it all second hand. Everything was pretty much below cost at that point with the sacrifice of not having brand new stuff. Lot's of people try to get rid of their stuff even if it's less than 6 months old. Maybe check it out?
Otherwise, good choices on your selections. Sounds like a good start to a "bumpin" system.
