Here is a handy chart which indicates that a 450w psu would be appropriate:
http://www.realhardtechx.com/index_archivos/Page362.htm
I have no problem overprovisioning a PSU a bit. Say 20%.
It will allow for a stronger future graphics card upgrade.
It will run cooler, quieter, and more efficiently in the middle third of it's range.
A PSU will only use the wattage demanded of it, regardless of it's max capability.
Of more importance is that you buy only a QUALITY PSU.
Here is one list:
Hello and welcome to the Motherboard tier list! This list ranks (or tiers) Motherboards from currently active sockets, namely the LGA1150, LGA2011-3, AM3+, FM2+ and FM2, separated by chipsets like X99, 990FX, Z97, H81, A88X, A55 etc. The ranking criteria comprise quality, usability and...
forums.tomshardware.com
I like the Seasonic focus in 450 or 550w