And then of course, right after I ordered the RAM, I saw on the product page that it was compatible with only the AMD 890 Series and AMD 790 Series chipsets. The A770E3 is an AMD 770 (Northbridge) and AMD SB710 (Southbridge). Should I just return the RAM when I get it?
i think you should still be fine,, usually it is just what they have tested and perhaps can't guarantee it.
You have already ordered it and will be charged a restocking fee whether or not you open the memory, so might as well give it a shot. G.Skill is one of the few manufacturers that make the memory most compatible with AMD chipsets and should be a safe bet.