Or if you want to go with a better processor and discrete graphics to be upgraded seperately later, i might do something like this:
PCPartPicker part list:
http://pcpartpicker.com/p/1kBiy
Price breakdown by merchant: http://pcpartpicker.com/p/1kBiy/by_merchant/
Benchmarks: http://pcpartpicker.com/p/1kBiy/benchmarks/
CPU: AMD FX-6300 3.5GHz 6-Core Processor ($109.99 @ Amazon)
Motherboard: Asus M5A97 R2.0 ATX AM3+ Motherboard ($94.98 @ Outlet PC)
Memory: G.Skill Ares Series 8GB (2 x 4GB) DDR3-1866 Memory ($72.99 @ Newegg)
Storage: Seagate Barracuda 1TB 3.5" 7200RPM Internal Hard Drive ($59.99 @ NCIX US)
Video Card: MSI Radeon HD 7770 GHz Edition 1GB Video Card ($94.98 @ Outlet PC)
Case: Antec Three Hundred Two ATX Mid Tower Case ($57.99 @ Microcenter)
Power Supply: Corsair Builder 600W 80 PLUS Bronze Certified ATX12V Power Supply ($37.99 @ Newegg)
Optical Drive: Asus DRW-24B1ST/BLK/B/AS DVD/CD Writer ($18.49 @ Amazon)
Total: $547.40
(Prices include shipping, taxes, and discounts when available.)
(Generated by PCPartPicker 2013-07-25 16:14 EDT-0400)
g-units build is a great option, i just wanted to highlight the other road as well.
EDIT: i just noticed you're in Canada, so these prices probably aren't spot on, but hopefully close.