Depends on the size of your case and your motherboard.
5770 beats the 6450 in every benchmark except power consumption
$539.99...well that's what it costs. It's worth will be defined if it does what you need it to do and how well it does that.
Yes. But I would reccommend buying a whole new graphics card, or at least the same, as the 6970 will have to downclock automatically, making it the same as a 6450
Sapphire HD 5450 is better than Sapphire HD 6450 .
Looking at your motherboard, the RX 480 will work with your rig no doubt. Just a suggestion, depending on what games you play, you could get a Geforce GTX 1050 Ti, as it is more than $100 dollars less, and can still run games very nicely with decent frames.
6450
322.5
21 divide into 6450 = 0.0032558139534883722
6450 meters = 21,161.4 feet
There are 5280 feet in one mile. Therefore, 6450 feet is equal to 6450/5280 = 1.221590 recurring (that is, 1.2215909090..) miles.
a millilitre is the same as centimetres cubed so 6450 :)
All My Children - 1970 1-6450 was released on: USA: 1994