Yes it will and with some(Quite a bit to be honest) power to spare.
I honestly thing it would be HARD to get the system to pull 420 watts with that hardware.
I can JUST pass 350 with OCCT stress test(the PSU one) one a 2600K @ 4.4 and 5870(both take more power)
You must mean capacitor aging over time for the power supply(lowering its output rating to 420 not increasing its draw to 420). Honestly I think it will take a while for it to happen, but yeah. I guess it would reduce over time. My bad if the above looked negative towards your post.