I'm a paranoid person so I'd personally stick with a 600w PSU but honestly 450w is plenty for what you're proposing. Unless you plan to have a lot of addons for this comp? Will you be using TV tuner, additional HDD etc with it?
500gb HDD actually runs out fairly quick... I'd recommend using at least 1TB hdd. (or better yet a small 64gb SSD with a 2TB HDD for storage).
Cheers.








