Upgrading GPU and PSU, what wattage should I go?
I bought A pre-build PC, (Asus CM6870) That came with a Nvidia Geforce GT 620, and a PSU of 300-350w PSU, and I had no choice to upgrade my GPU if I wanted to play games higher then the lowest settings possible in games, so what card would match a new PSU, that would be reasonable? I am thinking of something around a 650-750 or 700W, and if I am not using all of the power necessary for all my parts, where does the extra watts go? Do they just sit around? Thanks for the answers!
The psu max wattage is based mostly on the GPU. What do you plan to upgrade the GPU to?
The psu supplies the power needed up to the rated wattage. There is no "extra power" just extra capability.
Make sure the psu you get is a good brand. Antec, Corsair, Seasonic, or XFX.
The wattage doesn't actually mean anything, you can buy a $30 1000w PSU that will blow up in your face if you approach half that. Quality and amps do matter.
Basically buy from Silverstone, Seasonic, Corsair or Antec and you are good to go. You can run a top end single GPU setup on 500w, and a dual GPU setup on 700w.
If you buy a 1000w PSU, but your system only consumers 500w, then it doesn't just waste 500w as heat, it just doesn't use it.
At 650 to 750 watts, you can run pretty much any single graphics card you want easily.
A PSU draws only the power it needs for the tasks the computer is doing. Light surfing or watching vids, less power is drawn from the wall from the psu. On the other hand playing modern games or video editing will push your system and draw more power.
Here's a calculator to put you in the ballpark. http://www.extreme.outervision.com/psucalculatorlite.jsp