I bought the OC Radeon 6870 that was a one day offer last week. Its getting delivered today and now Im wondering if a Rasurbo 550 Watt power supply will be powerful enough for it. 
Currently Im finding that one of my two 14 cm fans on my case (randomly one or the other) doesn't start up without a little push and I was wondering if that was down to lack of power or something else. However I think its a relatively low power consuming system I have right now. Here are the rest of the specs..
Core i3 2100 cpu
Standard Intel cooler
4MB memory
2 hard Drives
4 case fans
CD writer

Currently Im finding that one of my two 14 cm fans on my case (randomly one or the other) doesn't start up without a little push and I was wondering if that was down to lack of power or something else. However I think its a relatively low power consuming system I have right now. Here are the rest of the specs..
Core i3 2100 cpu
Standard Intel cooler
4MB memory
2 hard Drives
4 case fans
CD writer

and have a fire extinguisher near you... Kidding
... but becareful ofcourse you never know with budget PSUs, they can go bang .. This is why I don't go down that route anymore I use to in the P4 days but the setups then were not as power hungry as they are now and would be fine on a cheapo PSU.
I actually checked two psu calculators and they are coming up with around 350 watt minimum so I have 200 watt buffer on top of that. However I have 2 12v rails. 1 outputs 19amp and 2 18amp. How does this convert to requiring a single 12v rail to be 20 watt? Actually those numbers that I mentioned are on the side of my power supply and conflict with the number on the article on that website for apparently the same power supply model.