If you are going to buy pre-built PCs, I don't recommend Alienware. I personally would recommend building your own PC.
PCPartPicker part list:
http://au.pcpartpicker.com/p/kNcrhM
Price breakdown by merchant: http://au.pcpartpicker.com/p/kNcrhM/by_merchant/
CPU: Intel Pentium G3258 3.2GHz Dual-Core Processor ($89.00 @ CPL Online)
Motherboard: ASRock H97M PRO4 Micro ATX LGA1150 Motherboard ($108.00 @ Umart)
Memory: G.Skill Ripjaws X Series 8GB (2 x 4GB) DDR3-1600 Memory ($91.00 @ IJK)
Storage: Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive ($68.00 @ Umart)
Video Card: Asus Radeon R7 260X 2GB DirectCU II Video Card ($155.00 @ CPL Online)
Case: Fractal Design Core 1100 MicroATX Mini Tower Case ($55.00 @ CPL Online)
Power Supply: Corsair CX 430W 80+ Bronze Certified Semi-Modular ATX Power Supply ($79.00 @ IJK)
Monitor: BenQ GL2460HM 60Hz 24.0" Monitor ($199.00 @ CPL Online)
Keyboard: Cooler Master CM Storm Devastator Gaming Bundle Wired Gaming Keyboard w/Optical Mouse ($46.00 @ CPL Online)
Total: $890.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2015-03-09 20:25 EST+1100