I'd spring the extra $35 and get the
i5-2500K - these things are probably the best 'bang for buck' CPU around, you can go up to 4.3GHz by just changing the multiplier, all on the stock HSF.
You won't need the extra PCI USB card, that motherboard already has 10 x USB2, (4 on the back, 6 on headers), ports and 4 x USB3, (2 on the back, 2 on headers), ports - so all you need is the backplane brackets if you require the extra ports.
Here's a USB2 one:

Regarding the case, (Ugh! - sorry

I prefer understated ones these days), since it's for a gaming rig - will you be carrying it around to friends and LAN nights?
If you are, then I'd recommend the
Cooler Master Storm Scout - a lot of space inside for your build, good cable management and carry handles.
If this is a stationary object that wont be going anywhere, then whatever floats your boat - although one that has front USB3 ports to take advantage of the headers on the motherboard would be good.
These days, I would not think of buying a case with less than either 3 USB ports, (2x USB2 + 1x USB3), or 4 USB2 ports available on the front. As an example, the
Fractal Design Arc Midi which also comes with fan controller.
EDIT: Carol snuck in ahead: +1 for Gigabyte, +1 for Noctua but if you can't afford the Noctua coolers, (in case you want something a bit better than stock), then the Cooler Master Hyper series are good, (eg. Hyper 212+).