radimax psu's are cheap crap. dont buy a crap psu, you will regret it. buy something from manufacturers who always use good components and produce overall reliable products like Antec, Seasonic, Corsair, OCZ, silverstone etc.
if that is your computer then you should perhaps just upgrade the video card to a 5570, since your cpu is slow and will bottleneck anything better. then you wont have to upgrade the psu also. you may need to call HP to find out if the gfx card is compatable.