400W is enough for your system but I have doubts on whether your PSU would actually be able to produce 400w of power continuously. I did a quick search on the PSU and it seems to be a relatively poor quality one and therefore I'd recommend upgrading your PSU before anything else as I wouldn't trust that PSU to power anything near 400w to be honest.
I'd recommend going for at least a half decent brand PSU, perhaps a Corsair or Antec with at least 500w rated power just to give you a bit of headroom for any future upgrades.