I'd personally go with a 450 watt psu that is 80+ bronze certified or better, I'm a fan of EVGA power supplies and i've never had a problem with them before.
Just a side note, I wouldn't recommend getting a gtx 950. With the rx 470, rx 460, and gtx 1050 right around the corner, if you wait a week or 2 longer you will be able to get much better performance for the same price.
just my 2 cents