If you want the most room in your case, go with an ATX form factor case- they are the biggest around to handle the longest (most high-end) video cards.
Use high-K light temps during veg (5000K+) and low-K for flowering (3000 or less) although by the time you reach flowering, you will probably need a more powerful light if you want a decent yield and it will probably have outgrown the PC case. have any plans on where you can transplant it?
Since you claim to be a newbie, I would recommend using strictly organic nutes. The pH isn't thrown out of whack by as large of a degree. Go with Earth Juice Grow and Bloom.
Also, I've heard bad things about Miracle Gro- it's got time-release nutes which mj doesn't like. You can just buy some really cheap soil with good stuff in it. forgot what i used before but I use Fox Farms Ocean Forest now and it's very popular (like $17 per 12qt. bag, pretty good).
And remember, it's called a weed for a reason. you don't have to water it every day. in fact, it thrives in low-water conditions. so don't flood it. that's the #1 mistake newbie growers make. give it a good watering every other day or so.