Hi, it seems dell 660s desktop has only 220 watts PSU (power supply unit), my question is , is this power supply really enough for a desktop computer? of course I agree dell being a standard company they will know how much is the minimum power needed for a desktop to run, but i am asking this so that i reassure myself that this paltry 220 watts is indeed enough, i am worried especially what will happen after a year or couple of years or so when there is generally the normal wear and tear with the battery and its efficiency and wattage decreases, will the battery still continue to provide adequate power supply to the computer even after a year or two? thanks!