New Build £900

[tjlld]

I have a £900 budget to spend on a new computer for gaming at 1920 × 1080. I am currently thinking of getting this:
YOUR BASKET
1 x OcUK HD 7950 3072MB GDDR5 PCI-Express Graphics Card - AMD 3 for FREE Promotion £239.99
1 x Intel Core i5-3570K 3.40GHz (Ivybridge) Socket LGA1155 Processor (77W) - OEM £167.99
1 x Microsoft Windows 7 Home Premium SP1 64-Bit - OEM (GFC-02050) £83.99
1 x Gigabyte Z77-D3H Intel Z77 (Socket 1155) DDR3 Motherboard £82.99
1 x SanDisk Extreme SSD 120GB 2.5" SATA 6Gb/s Solid State Hard Drive - (SDSSDX-120G-G25) £77.99
1 x Cooler Master Silent Pro Modular 600W '80 Plus Bronze' Power Supply £65.99
1 x Antec 300 Three Hundred Ultimate Gaming Case - Black £44.99
1 x **B Grade** Seagate Barracuda 7200.12 500GB SATA 6Gb/s 16MB Cache - OEM (HD-252-SE) £40
1 x GeIL Dragon 8GB (2x4GB) DDR3 PC3-12800C11 1600MHz Dual Channel Kit (GD38GB1600C11DC) £33.59
1 x Gelid Tranquillo CPU Cooler (Socket 754/939/940/AM2/AM2+/AM3/LGA775/LGA1155/LGA1156/LGA1366) £25.99
1 x OcUK 22x DVD±RW SATA ReWriter (Black) - OEM £12.98
Total : £891.48 (includes shipping : £12.50).



Any recommended changes much appreciated.

 

[tjlld]

I am not sure I actually need Xfire as I will probably not upgrade in the next 3 years. In a few years time will it still be possible to get 7000 series graphics cards?
As for the motherboard what disadvantages come from getting B grade? Would I have to buy some screws and wires?

 

[tjlld]

Thanks for the help.
The only thing I am not sure on is the case.
Other people seem to be recommending the Xigmatek Asgard Pro Gaming Case which is also £10 cheaper.
Another option is the BitFenix Merc Alpha Gaming Case or BitFenix Shinobi USB3.0 Gaming Case?
How do these cases compare with the Antec 300?