with a 7800gtx your going to need a bigger budget. the 7800gtx is about 800,case about 70,going to need a good PSU 100, mobo 150,HDD 100,120 for RAM,CPU 250,monitor at least 100,speakers at least 20=$1710 canadian which is about $1,411.61 US thats without tax and shipping.
this isn't ment to put your plan down but your going to have to reduce your graphic card to get a system for that price.
CPU-Intel Pentium 4 630 3.0Ghz / 2MB Cache ~~OS Windows XP SP2
MOBO-Gigabyte 8I915P Duo Pro Intel Socket 775 (PCI-E)~~HDD-Western Digital 160GB(SATA)
PSU-Aspire 500W ATX~~RAM-1GB PC3200 DDR SDRAM (512x2 Dual Channel)
GPU-MSI GeForce 6600 GT(PCI Express)~~Monitor Viewsonic VA902B 19" 8ms~~ ATI TV Wonder Pro (TV Tuner)
~~Still to come~~: eVGA e-GeForce 7800 GT