Gaming rig - budget aprx£550

APPROXIMATE PURCHASE DATE: Next month or so

BUDGET RANGE: £500 (he may stretch it to more)

SYSTEM USAGE FROM MOST TO LEAST IMPORTANT: Gaming and some minor programs

PARTS NOT REQUIRED: keyboard, mouse

PREFERRED WEBSITE(S) FOR PARTS: any really but prefer aria.co.uk

COUNTRY OF ORIGIN: england

PARTS PREFERENCES: no major preference

OVERCLOCKING: probably not

SLI OR CROSSFIRE: probably not

MONITOR RESOLUTION: unsure

ADDITIONAL COMMENTS:
I am building this PC for a mate and therefore trying to tell him the benefits of spending extra for quality parts but he is keen to keep the cost low as possible. He wil be running cod2 and BF2 mostly and is just aiming at a reasonably high rate of fps.
he is keen to stick around the £500 mark but may go up to £600 if necessary. Thanks in advance!!

Build ideas so far;

MOBO: ASRock M3A770DE AMD770 (Socket AM3) = £56
http://www.aria.co.uk/Products/Components/Motherboards/...

GPU: XFX ATI Radeon HD 5750 512MB GDDR5 = £92
http://www.aria.co.uk/Products/Components/Graphics+Card...

CPU: AMD Athlon II X2 Dual Core 250 3.00GHz = £53
http://www.aria.co.uk/Products/Components/CPUs+%2F+Proc...

PSU: OCZ StealthXStream 500W Silent = £45
http://www.aria.co.uk/Products/Components/Power+Supplie...

CASE: coolmaster elite 330 = £29
http://www.aria.co.uk/Products/Components/Cases/MIDI+To...

MEMORY: (bit unsure on this one as RAM is so expensive atm) 1066Mhz 240pin 1024MB PC3-8500 DDR3 Memory = £45 (3 units of this ram)
http://www.novatech.co.uk/novatech/prods/Components/Mem...

HDD: Samsung HD322HJ SpinPoint F1 320GB = £32
http://www.aria.co.uk/Products/Components/Hard+Drives/S...

OS: windows 7 profesional = £30

MONITOR:Fujitsu 20" Widescreen LCD Monitor = £84 (dont think he is too bothered about a 1920 res)

TOTAL = £466

I think there is room to improve some items within the budget there. Im thinking RAM but let me know what you guys think.  

Thanks