no the 620hx is getting hte extra 100watts from another rail which you shouldn't care about unless you plan on getting a lot of hard drives and a lot of Peripheral Devices and stuff to put in your PCI slots
plus things are going DOWN in power consumption, take my Pentium 4 to a Core 2 Quad qx9770, this is the biggest power sucker of the series... and my Pentium 4 is single-core and consumes more power and high on temps