First Custom, Need Feedback

Hello all. After some research and restless nights I have finally put together a hotlist for my first custom PC. Unfortunately, I do not really know enough to prevent myself from making mistakes. If you guys could take a look at the specs below and provide some feedback I would greatly appreciate it.

To provide some context, I use my PC for gaming, but not competitively. I also rarely get involved with graphical monsters like the Crisis series. Something which will own Sims 3 and Diablo III when it comes out should suit my needs fine. Thanks in advance!

POWER SUPPLY: 420 Watts Standard Case Power Supply

CPU: AMD Phenom™II X4 955 Black Edition Quad-Core CPU w/ HyperTransport Technology

COOLING FAN : AMD ATHLON64
CERTIFIED CPU FAN & HEATSINK

MOTHERBOARD: Asus M3A76-CM AMD 760G Chipset DDR2/1066 SATA RAID PCIe Mainboard w/ATI 3000 Graphic, GbLAN, USB2.0, & 7.1Audio

MEMORY: 4GB (2GBx2) PC6400 DDR2/800 Dual Channel Memory (Corsair or Major Brand)

# VIDEO CARD: NVIDIA GeForce 9500 GT 1GB 16X PCI Express (Major Brand Powered by NVIDIA)

HARD DRIVE: Single Hard Drive (500GB SATA-II 3.0Gb/s 16MB Cache 7200RPM HDD)

Optical Drive: LG 20X DVD±R/±RW + CD-R/RW DRIVE DUAL LAYER (BLACK COLOR)

SOUND: HIGH DEFINITION ON-BOARD 7.1 AUDIO

NETWORK: Onboard Gigabit LAN Network

USB PORT: Built-in USB 2.0 Ports

OS: Microsoft® Windows Vista™ Home Basic w/ Service Pack 1 (64-bit Edition)

Power Supply.

First, not enough power.

second, get a BRAND NAME power supply like Corsair, Antec or BFG.

A no name power supply can KILL your whole system...

(Last part you want to skimp upon)

I won't go below 550W myself.

+1