There are a billion things it could be, not least of which is the fact that youve switched graphics cards, and possibly left some traces of drivers from the old graphics card lying around in the system.
Try using driver cleaner pro or driversweeper to completely remove your old card's drivers, then reinstall the drivers for your new card. No guarantees this will help, but it's always worth a try if you have problems after switching cards.
Before you try that however i'd recommend following Prodigal's advice - turn all of the graphics settings down to minimum and see if the problem goes away. If it does, try turning them up gradually to identify the problem area. Bear in mind that a $99 graphics card isnt top of the range and so may not be able to handle everything ETW can throw at it.
Edit: Oh, also, youre more likely to find help at these places:
Apothecary
Official ETW Hardware Problem Solving Thread
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