Edit: If you aren't sure why I ask this, answer this. Can a car with four wheels go 150MPH? Depends on the car of course. Can a 450W PSU power a Athlon 640 with who knows what else? Depends on the else and the PSU.
Should be fine. A low end/junk 450W might have issues with the load but most 450W PSUs should be fine. Your load for that system should be less then 200W, so assuming the 450W PSU can output at least half its rating you should be fine.