Serious upgrade - on a budget

AMD Athlon64 X2 5000+ Dual Core (2.6GHz) - AM2, HT 2000, 2x512kB L2 Cache, G1 Stepping, 65nm, 65W - Boxed

MSI K9N-SLI-F-V2
AM2, nForce 570LT SLI, HT 2000, 4x DDR2-800, 2x PCI-Ex16, 4x SATA-II, RAID, GigLAN, 8Chl, ATX

Team 2048MB (2 x 1024MB) PC2-8500 1066MHz DDR2 RAM - 5-5-5-15 - Xtreem Dark Series

Palit Geforce 8800gt 512mb

Antec Super Cyclone Blower - Dual Expansion Slot Cooler

CoolerMaster eXtreme Power 500W PSU - ATX v2.01

$67.10

and by the way i live in melbourne, australia so this site is just a reference for what products im interested in, id actually be buying everything from a shop rather than online.

Well its been a while since ive been thinking of upgrading my current rig : P4 1.8ghz, acer mobo, 512mb ddr ram, ati radeon x800 pro agp 4x, 300watt power supply.

and i tried to assemble a couple of components myself. I know amd isnt the best one to opt for at the moment but considering my budget that the best i could find ?

perhaps it is OKAY ? anyways i would like my fellow gamespotters to comment on the rig, and also i had a couple of questions with assembling the system myself. the thing is that im just gonna upgrade my current pc so im still gonna use my current acer case, mouse, 17" crt monitor, case, etc., but ive never assembeled a system myself(but i know how to do it), so i was wonderingjust wondering that will i stuff up while installing the ram with the timings and everything (im not an expert with bios settings) all i can do is assemble the stuff and run windows(but i am not aware of what all do i need to do in the bios)

so if someone can plz let me know what exactly is involved after i assemble the components to have my pc up and running, id really appreciate it.

thanks

will i be able to run games like crysis, gears of war, assasin's creed on highest settings at low resolutions (800x600 ?)

or should i just do justice to myself and go for a xbox 360

You should have no problem, You can easily play crysis with all high 2x AA at 30 FPS on 1024x768 or at around 20-25 FPS at 1280x1024.

Nice build for hte money :)