Currently I own a 5770 videocard (which I havent tested yet) and my PSU is a quite old 550W model with 24A in the 12V. One friend says that such PSU is not enough to properly feed the card and Im taking the risk to burn it, is that correct? What he seems to dislike most about the PSU is that it is not a recognized brand, but I have been working with it for around 2 years, with other video cards like my previous 4770 without problems.
Also, Im thinking about changing to a GTX 460, which requires some more power, is that PSU enough or should I change it before going for the 460?
I run my system with a HD 5750 of a 380W PSU, even though according to AMD's system requirements I should be using a 450W PSU. I have yet to see my total system power consumption exceed 160W.
Having said that. I do have a quality brand PSU that can deliver more AMPS on 12v then yours. And I do agree with your friend that you should really buy a quality brand PSU, preferably one of these 80+ ones.
The main thing to be aware of when dealing with cheapass power supplies is that when they blow, they have the potential to destroy EVERYTHING. I've seen it happen -- power supply blows, and takes mainboard and hard disk with it.
Given though that this one has worked for a couple of years, it probably isn't going to blow so spectacularly. I came across a bunch of nasties that started going within DAYS of new. The vendor of those machines ended up having to suck it up -- there were about a dozen machines total, and three of them were totally destroyed. They all ended up with new brand name power supplies at no extra cost since we said to either put in the good ones, or he'd be warrantying all of them every couple of weeks until he is convinced.