Test and verify
Use what HP offered as in any video upgrade as a clue to what will work with ease. Don't over-analyze this and it maybe better just to have the PC working then check results "as is". Robert, offers the 5450 as a good video card to what seems to match your needs and overall isn't expensive. Otherwise, you maybe better off replacing the PSU once a high-end video card is installed. Take my word for it, cheap is cheap, so if cost is your over-riding factor beware of the possible result. Also, cooling is very important in a heat stressed system for "everything" if video card is power hungry and demanding.