Well, the 5450 pull considerably less current that the 7970 does, so it could possibly be the PSU. Corsair PSUs are a top brand, and I own 4 of them right now. But, any of them can go bad. It's rare for a Corsair to go bad, but it does happen. You gave me the voltages from bios and were fine. But, that only tells what they are at idle, not what they do when under a strong draw. The 5350 won't pull very much power. What brand 7970 do you have?
As far as trying Beta drivers, absolutely. When you are looking at an RMA, I would try any drivers to see if it makes a difference. Beta drivers and even older drivers would be worth a try.
I don't know what brand hard drive you have, but I would run the manufacturer's diagnostic program for it. Seagate's is here
SeaTools for DOS | Seagate
Western Digital's is here
WD Support / Downloads / SATA & SAS / WD Black
You will get better results running the DOS version and running the Short drive self test and the long drive self test.
You can use this to help test the power supply, but it will be difficult to test it under a high stress situation.
http://www.sevenforums.com/tutorials/301799-psu-test-dc-output-voltage.html
There is no test I know of which will test the motherboard. It is normally a process of elimination. If everything else in the computer checks out, the only thing left is the motherboard. I don't believe there is any incompatibility issue. The board has an X16 slot and as far as I know, it works or it doesn't.
I would also try a different cable from the card to the monitor before an RMA. Sometimes the cable can be bad also.
I would also consider this To try to tell what is happening with the card. It will tell you almost everything that is happening inside your card. The log can be quite long, so as soon as you start it, do whatever will cause your card to crash as soon as possible. I use Ungine Heaven 4.0. It will stress the card pretty heavily. Probably more than any game you will play. Turn it off as soon as you can to stop it from logging. You can go back to where the card crashed and see what changed immediately before the crash. This will explain it.
http://www.sevenforums.com/tutorials/330579-graphics-card-problems-diagnose.html
EDIT: I also noticed the screenshot of Speccy. If you were just idling, the 47C is high for your CPU. If under stress, it is not too bad. At idle, you should be somewhere in the 30C range.
I saw where you ran memtest. which version did you use and did you download it from this site?
http://www.memtest.org/