Hi guys I have been looking at getting one of these cards. I have an MSI board in mind and would like an MSI gpu. I would just like to know witch one is the best value for money or just if its wourth getting the BIG one. The R7990-6GD5
R7970 TF 3GD5/OC BE or R7970 Power Edition 3GD5 or R7970 TF 3GD5 BE or
R7970 Lightning BE
Honestly I wouldn't consider the 7990 until the frame pacing driver comes out, which should be late July or early August. There are stuttering issues that need to be addressed with that driver.
Out of the other cards you mentioned the Lightning should be the best overclocker. If you don't plan to overclock very much, then the cheapest of them should be at least able to match the lightnings stock settings.
If you have no plans at all to overclock the lightning/power edition will have better stock performance then the others, but at a higher price.
I personally would buy the cheapest of the cards and overclock to match the lightning manually. That way you get the best bang for buck. The 7900 series are known to be really good overclockers, and most i've seen reviewed hit 1100-1200mhz core clock quite easily if you up the voltage a tad bit.