In Flames we trust

This build looks pretty good! Though I would go with a good 600W PSU just so you have the headroom should you want to upgrade in the future. Also, for just an extra $10 you could get an FX-8320 (8 cores instead of 6). In terms of optical drives, they're all pretty similar and really cheap, so you can get by with anything. The only real difference between them is some are blu-ray drives, which are pretty pointless anyway. Looking at this website, you can get an XFX Radeon HD 7870 for a little cheaper than the 7850 too.

1) When looking for a case, you want to look for features (i.e. USB3, multiple fans, fan controllers, dust filters, etc.), size and what the case is compatible with: sizes are full tower (large, lots of room for expansion and the most features but the most expensive), mid tower (not as large and not as much room for expansion but affordable, imo mid towers are the best to go with) and micro ATX/mini ITX cases (small, hardly any room, probably should avoid), and airflow (does it have a lot of ventilation and fan mounts?)
2) Quality. Do NOT cheap out on the power supply, it's like the heart of your computer. If the power supply is too weak and can't supply enough or clean power to your components, your PC is gonna have a lot of problems. Look for 80+ bronze certified power supplies at least. Also, depending on what your budget is/what components you're getting, you'll want to look at how much power a PSU can give. E.g. if your PC has a quad core and a single medium level graphics card such as a Radeon 7850, you can get by with a 500W PSU. However, if you're going to have multiple graphics cards and a lot of overclocking, you're gonna want more Watts. General rule of thumb, buy a little bit more than what you need when it comes to a power supply. You can also look in to modular power supplies which allow you to remove cables you don't need to reduce clutter and have a tidier build, but it'll cost a bit more.
3) I've configured powerful AMD 6 core PCs at around £400 ($600-ish?) before which are more than adequate to run TF2 at max settings (trust me guys, AMD isn't that bad, especially because future games are looking to be more AMD optimised).
4) You want to invest the largest amount of money on your graphics card, followed closely by the processor. The graphics card is going to be doing most of the work when playing games, followed closely by the CPU, so make sure these 2 components are focused the most.
5) No. There's a lot when it comes to compatibility, for instance, you cant put an AMD CPU on an Intel motherboard, a full ATX motherboard wont fit inside an ITX case, etc. etc.

I could go in to more detail, but it'll take a while and I already know this is a tl;dr scenario, so add me on steam if you want more help: http://steamcommunity.com/id/larvalextract/

Overall, dont start building until you have a solid budget; it's not all about performance, it's about price/performance ratio (the best bang for your buck), and read as many reviews on separate components as possible! Hope this helps :)

Actually, the FX-8350 is a very viable option for live streaming, thanks to its very impressive multi-thread/multi-tasking performance. It's been tested and proven to perform as good as or better than a Core i5/i7 equivalent when it comes to streaming games: http://www.youtube.com/watch?v=eu8Sekdb-IE (he tested Black Mesa Source which is close enough to TF2). Also, it costs a lot to upgrade to Intel seeing as you'd need a new motherboard. Imo, I think the AMD is a better option as it's cheaper in the first place and you're already on AM3+.

http://www.kaize.co.uk/media/garbage/scoreboards/larval_6_doms.jpg

i48 playoffs

http://www.kaize.co.uk/media/garbage/2013-06-16_00002.jpg

skial harvest shenanigans