I'm planning on getting a new GFX card tommorow. Since I'm on a budget, and am able to get a 5770 for just 150 euros, I thought it would fit my system just fine. However, I'm kinda worried that my PSU won't be able to handle it, since the ATI website recommends 450W or higher for the card. These are my system specs:
It's not about total watts, it is about how many amps the PSU can supply on the 12 volt rails. That PSU will run a 5770 just fine. The reason they say 450 is because at 450 total watts, even a cheaply made generic PSU should have enough juice to run the card. A well made brand name PSU like you have will supply a hefty dose of good clean power even though the overall wattage is not as high as what is recommended on the box.