1 - Why do you need the network card?
2 - If your monitor is 24" and you want great performance, you should consider up-grading your GPU. GTX 560 is great, but depending on AA and AF, it can get slow @1920x1080. Should you decide to stick to it, don't waste time getting the OC card, unless the price difference is minimal. OC it yourself and save some cash.
3 - I suggest getting a full tower case. Later on, when you want to SLI, or decide to get a bigger GPU, it will be better. Plus, it helps lowering your temps today.
4 - +1 on your PSU x mobo: you either up-grade you PSU (750W) or down-grade your mobo.