Which computer for gaming?

ok well i have a few options, i would like a computer that will be able to handle games on the highest settings without overkill and buying stuff that will never get used, that said here are the options and prices next to them(also price is a factor) Genuine Windows 7 Home Premium (64-bit) for superior digital... show more ok well i have a few options, i would like a computer that will be able to handle games on the highest settings without overkill and buying stuff that will never get used, that said here are the options and prices next to them(also price is a factor)

Genuine Windows 7 Home Premium (64-bit) for superior digital entertainment
Intel® Core™ i5-2400 processor for incredible performance
6GB memory for top system performance & running multiple applications
1.5TB hard drive for storing all of your digital files
"AMD Radeon HD 6850 (1 GB GDDR5 dedicated) with Avivo technology"
USB Keyboard and Mouse
DVD writer SATA DVD RAM and Double Layer its about £1300 inc monitor

Alienware (not sure if it is worth the price just for a brand name possibly) it is the Aurora, 3.4GHz Intel® Core™ i7-2600 (8MB Cache) Quad Core Processor with overclocked Turbo Boost to 3.9GHz, 1.5GB NVIDIA® GeForce® GTX 580, 8192MB (4x2GB) 1333MHz DDR3 Dual Channel Memory, 2TB RAID 0 "Stripe" (2x1TB - 7,200 rpm), DVD+/-RW (Read/Write) 24x, Integrated HDA 7.1 Dolby Digital Audio, Dell 1525 Wireless PCIe Network Card 802.11n, 23in ST2320L UK/Irish Full HD WLED Widescreen Monitor (VGA, DVI-D and HDMI), Logitech® Z506 5.1 Surround Speakers - 75W Total, alienware mouse, alienware keyboard about £1750

XPS 8300
i.7 2600 processor
2TB hard drive
12GB RAM
NVIDIA® GeForce GTX 560 Ti 1.25GB GDDR5 Graphics Card
23in ST2320L UK/Irish Full HD WLED Widescreen Monitor (VGA, DVI-D and HDMI)
Blue Ray Optical Drive about £1400

ok so there they are, oh another question is alienware as overrated as many people say it is? i would rather pay more for a better computer that will last longer but i dont want to spend too much if it is not necessary,
ok guys thanks for reading i would appreaciate all the help i can get :)
Update: * im english so cant go to newegg and i am looking for a desktop not a laptop which of these is the best? was what i meant by my question :/
Update 2: where would i buy the components from though as newegg dont ship to england, do they?
Update 3: can you suggest what i should choose i.e. which case, power supply.. and a list of what i need to make a fully functional computer please?
Update 4: ok, if i can't build one would this be better http://www.aria.co.uk/Systems/Gaming+Range/Gladiator/Gladiator+Deathwing+H20+Intel+Core+i5-2500K+%40+4.60GHz+DDR3+Gaming+PC+?productId=47226
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