New Rig Help?

Hey
I'm thinking about building a new computer (my laptop is slowly showing its age!) - I'm sure I have all the parts I need but could someone please have a look and see if what i'm buying is a) Any Good b) compatible with the rest of the build
I'm trying to get as much power out of it as i can without spending a fortune (I realise how hard this will be ) Any hoo this is my build, by the way is CCLonline a descent store?

CASE

Avenge Power Black & Sliver Tornado ATX Case

£ 27.79

http://tiny.cc/0g2it

PSU

500W Xigmatek NRP-PC502 Power Supply

£ 48.03

http://tiny.cc/1olpe

MOBO

Gigabyte GA-MA785GT-UD3H AM3

£ 71.99

http://tiny.cc/kck75

CPU

AMD Phenom II X2 555 Dual Core

£ 86.16

http://tiny.cc/kx1ms

RAM

4GB CCL Choice 1333MHz DDR3

£ 82.98

http://tiny.cc/0o0d7

GPU

CCL Choice GeForce GT 240 1GB

£ 65.57

http://tiny.cc/3onw6

ODD

Sony AD-7240S-0B 24x DVDRW

£ 15.25

http://tiny.cc/x8qdg

HDD

500GB Hitachi Deskstar 7K1000.C 3.5"

£ 34.58

http://tiny.cc/xk6os

WIFI

TP-Link Wireless-G PCI Card TL-WN350G

£ 7.23

http://tiny.cc/8fcbr

INPUT

Microsoft Wired Desktop 600 USB

£ 17.57

http://tiny.cc/fqfje

DISPLAY

20" BenQ G2020HD Widescreen Monitor

£ 103.82

http://tiny.cc/fm7qw

I would go up on your power supply for sure.

You got a gig of gaming power so i am thinking in the future you may want to expand.

You can never go wrong with a bigger and better power supply.. because remember
without power, your in the dark.

2nd...umm if you can spare the change.. go with a little better processor. Check the MB specs and see what else it can handle or if you can go up to at least a quadcore.

OK "Deathstar" removed - i'm assuming this has a short lifespan Samsung added :)
Okies - I did have my doubts about the processor Anybody think an AMD Athlon (I or II) Quad Core would do? Someone told me they werent too good so I avoided it
Looking at PSU's also, what kinda wattage u think wud do it? Thanks for help so far btw