Budget Gaming Build - Stuck On Some Things

Well after almost four years with my current computer and I've decided I need a new one to handle the 1920x1080 resolution my monitor uses in games. Well after several hours of looking into different parts I have got most of the parts but I am stuck on several parts due to the fact this I my first go at making a pc from scratch  


APPROXIMATE PURCHASE DATE: This week hopefully

BUDGET RANGE: £450/$682

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Gaming, Watching movies

PARTS NOT REQUIRED: keyboard, mouse, monitor, speakers, OS, Hard Drive

PREFERRED WEBSITE(S) FOR PARTS: Scan www.scan.co.uk, Amazon UK www.amazon.co.uk

COUNTRY OF ORIGIN: UK

PARTS PREFERENCES: No preference

OVERCLOCKING: No

SLI OR CROSSFIRE: No

MONITOR RESOLUTION: 1920x1080

ADDITIONAL COMMENTS: I have already found several parts I want to get, they are:

Case - Antec Three Hundred Midi Case, http://www.amazon.co.uk/gp/product/B0017Q8IAA/ref=ord_c... - £ 43.99

CPU - Intel I3-530, http://www.scan.co.uk/Products/Intel-Core-i3-530-Dual-C... - £91.80

Motherboard - Gigabyte GA-H55M-UD2H, Intel H55, 1156, http://www.scan.co.uk/Products/Gigabyte-GA-H55M-UD2H-In... - £69.97

Graphics Card - Radeon HD 5770, http://www.scan.co.uk/Products/1GB-XFX-HD5770-PCI-E-20%... - £129.92

So as you can see I still need a PSU and some RAM (DDR3 4GB 1600MHZ) that will fit in with my budget. Any help with this would be great as I have no idea which kind of PSU to get all I know is that I need at least 500W.

And I am half a sleep writing this so sorry for any errors