I currently have a Pentium 4 3MHZ CPU, 1GB of RAM, 200 GIG hardrive,DVD drive and DVD re-writer and a X300 graphics card all powered by a 300W PSU. I want to increase memory to 2GB of RAM in order to play Fear and Oblivion.I also want to upgrade the graphics card. I note that the 7900GT usually requires a 350W PSU, and the 7600 is a lot smaller, but I cannot find any info on a desired PSU for this card. I can just about afford the 7900GT, but I wonder whether this will overstretch the PSU?.If so will I be OK with a 7600GT?. I do not want to buy a new PSU as the same is on a HP deal, which allows minor upgrading ie RAM and Graphics card. Any ideas?
To be honest with you I have to agree with Mr Mistoffelees whichever card you use I do not think the power supply will be able to cope. It might but I really doubt it. Have a look at this and bear in mind its a bit out of date with power ratings but it'll give you an idea click here
If you have a good quality psu such as an Antec or other named brand your 300W might just about be adequate........but it will be pushing its maximum output most of the time when gaming.
An update to give some headroom to 400W or above is desrable.But if replacing the psu is not an option go for the 7600GT.It outperforms my ATI X800XT easily....and mine has played both FEAR and Oblivion at decent settings.
Of the two graphics cards the 7600 will be less power hungry and will play the games you mention well...providing you stay clear of antialiasing and high levels of anisotrophy.The 7900GT is much more capable of handling aa/af than the 7600GT but more demanding of both memory and the psu as a result.
Neither will play the games maxed out so go with the 7600GT and have £60 to spare for more games......you will be amazed at the improvemrnt over the X300 graphics!