although id say id look at around 500-650W because they sometimes can be cheaper then 450W due to them being more in stock and sales from the excess.
I second davey's brand recommendation minus thermaltake. Seasonic, EVGA, Corsair, Silverstone, Super Flower, Lepa.
I would AVOID Gigabyte like a plague tho.
Make sure its at least bronze rated, silver is where im more comfortable with budget builds, and Gold is where i piece most of my builds unless its going to have a monster class GPU, which then its only platnium/titanium.
And please do not try to go too cheap on the PSU.
Its essentially the one and only piece in your entire system that if it should go bad, it can and might take out every last component along with it.