Either type will work fine. If you're purchasing one, get a quality name brand, even if it's rated lower in wattage. Cheap power supplies do not hold up under load; I've had some die in days. I recommend antec, enermax, seasonic, corsair, or pc power and cooling. 500 watts with one of these brands should be sufficient for a one video card system; 700-800 for 2 high end cards.