|As riider said|
'The HD 6450 is a low end card. It's OK for general purpose/home theater use, but it's not much of a gaming card."
See the last two parts of response 2.
I recommend you buy a video card with the best performance for a price you're willing to pay, but keep in mind you must determine what the minimum recommended power supply is for the video chipset.
On top of that, when you search for a video card with a particular video chipset, this time of year there are often some sales or mail-in rebates for some of them.
If your power supply's capacity is already, say, 500 watts or more, you probably don't need to buy one with more capacity for any single video card these days.