[Kayen]

Prices are before rebates.
Build 1 Here we go:
Reuse optical drive & case.
Mobo/CPU: NCIX.com - Buy NCIX Value Bundle Deal AMD Athlon II X2 245 & Gigabyte MA785GM-US2H DDR2 Motherboard -UNASSEMBLED - 785GM-X2-245 In Canada. $155
PSU: NCIX.com - Buy Seasonic M12 II 500W EPS12V 20/24PIN ATX Modular Power Supply Active PFC 80PLUS 6PIN PCI-W 120MM Fan - SS-500GM In Canada. $75
RAM: NCIX.com - Buy Patriot Extreme Performance 4GB 2X2GB PC2-6400 DDR2-800 CL4-4-4-12 EPP Dual Channel Memory Kit - PDC24G6400LLK In Canada. $68
HDD: NCIX.com - Buy Western Digital Caviar Black 640GB 7200RPM 32MB Dual Proc 3.5IN SATA Hard Drive OEM 5YR Mfg Warranty - WD6401AALS In Canada. $76
$374 before taxes + s&h.

Built 2:
MOBO: NCIX.com - Buy Gigabyte GA-MA770-UD3 ATX AM2+/AM3 AMD770 PCI-E16 2PCI SATA2 RAID 1394 HD Sound GBLAN Motherboard - GA-MA770-UD3 In Canada. $88
PSU: NCIX.com - Buy AMD Phenom II X4 955 Black Edition Quad Core Processor AM3 3.2GHZ 8MB Cache 125W 45NM Retail Box - HDZ955FBGIBOX In Canada. $290
CASE: NCIX.com - Buy Coolermaster cm 690 Mid Tower Black ATX Case 5X5.25 5X3.5INT No PS Front USB Sound Firewire & eSATA - RC-690-KKN1 In Canada. $86
PSU: NCIX.com - Buy Seasonic M12 II 500W EPS12V 20/24PIN ATX Modular Power Supply Active PFC 80PLUS 6PIN PCI-W 120MM Fan - SS-500GM In Canada. $75
RAM: NCIX.com - Buy Patriot Extreme Performance 4GB 2X2GB PC2-6400 DDR2-800 CL4-4-4-12 EPP Dual Channel Memory Kit - PDC24G6400LLK In Canada. $68
HDD: NCIX.com - Buy Western Digital Caviar Black 640GB 7200RPM 32MB Dual Proc 3.5IN SATA Hard Drive OEM 5YR Mfg Warranty - WD6401AALS In Canada. $76
Video: NCIX.com - Buy ASUS GeForce 9600GSO V2 550MHZ 512MB 1.4GHZ DDR3 PCI-E VGA DVI HDMI HDCP Video Card - EN9600GSO/DI/512MD3/V2 In Canada. $60
OPTICAL: NCIX.com - Buy LG 16X DVD-ROM Drive Internal SATA OEM - DH16NS10.AVAA10B In Canada. $24

$767 before taxes and shipping, however if you pricematch i'm sure it'll be able to come down a bit.
I got the Phenom X4 955 for $220 from DC. Use price canada's engine right here on HWC .