I have a similar setup and have the 520HX and I use about 160W at max(I have a piece of hardware that monitors this).
I also want to stress if you are looking to buy a PSU you want to look at a few factors like the amperage on the rails more than the total watts you can obtain, especially on the 12V rail.
Another thing is name brands, you want something with more clout rather than a no name.