You should be ok with your current PSU.
When installing a new GPU, you first should un-install current/old graphics driver. The easiest way is to un-install is from the device manager. Here's a link from AMD how to go about it.
When you physically install the new GPU and boot up the system, you should have loaded in the cd/dvd bay the provided install disc which has the software (CCC panel) and driver on it. Or go to the vendors website and get the latest version. Just putting the card in and letting windows use the generic drivers is a really bad idea. Here's a link for the latest AMD drivers for your card.
Note: Kaspersky AV is known to cause BSOD's and crashes.