280 watts is indeed very light. You might want to take a look at this page and run a calculation on what power your hardware actually draws. If it comes to more than 280 you're heading for trouble.

educations.newegg.com/tool/psucalc/index.html

Expert in computer code including, but not limited to, BTW; IIRC; IMHO; LMAO; BRB; OIC; ROFL; TTYL. Black belt in Google-fu.