Upgrading an Older Desktop [PSU and GPU]

[Deleted]

Hello all,

I am looking to upgrade an aging HP desktop (the a6325.uk, motherboard similar to this) to make it perform better with the occasional gaming task. The games that will be run on the machine aren't too intensive (World of Warcraft, Half-Life 2) yet could benefit from a more powerful GPU I feel. In undertaking this upgrade I realize I will need to upgrade the PSU.

Are there any particular things I should look for when purchasing a new component with a higher wattage? Should the majority of components work with the micro-ATX board and case design?

I am not looking to draw too much power and have been considering:

Corsair 430 W
or
OCZ 500 W

In addition to bumping up the PSU, a new graphics card is in order. Space in the case is limited (this is kind of a deciding factor and I will need to recheck my dimensions) and I have been contemplating between:

AMD 6670
or
an AMD5670 if I can find one.

Any graphics cards suggested shouldn't be longer than around 17cm and single slot size only. Cards which do not require external power (additional pins) are preferred due to the annoying case design.

I have not upgraded the RAM (3 GB) in the machine nor the processor (C2D E4500). These are areas which I will be considering in the future. I do not need to run the games on max settings - currently with things on medium I see 25 to 35 fps in raids using the 8500 GT and would just like to make this performance a little smoother. Gaming is something I do not have a huge amount of time for at the moment so upgrading to a much better machine seems kind of futile as any other complex tasks I run are undertaken on a Linux cluster.

All further suggestions and advice welcome. Thank you for your time.