I am intending on upgrading my Compaq's GT120 GPU to a HD5670 GPU but I currently only have a 300W OEM PSU. I have checked with my local hardware forums and members have indicated that I do not need to change my PSU to to allow my new 5670 to work, but I wanted to be safe so am considering to buy a new PSU: Cooler Master Silent Pro 500W.
Now the problem is the installation. I have a top-mounted PSU with the fan pointing out of the case while the new CM PSU will have the fan on the top side. So can I flip the new PSU around so it will point its fan into the case or else the fan will be blocked by my case. If you don't know what I mean is it the same as this case: http://www.fonerbooks.com/r_power.htm
The fan will not be blocked it still will have about a 1\4 inch of clearance which is enough. The fan sucks air from inside the case and expels it out the back it will be fine, but yes you can mount it any way you like as long as its in the case that's all that matters.
No the new power supply will not consume more energy it will actually use less because it has a better efficiency rating. The power supply only pulls from the wall what is needed.