I'm just gonna leave this here...

http://forums.overclockers.co.uk/sho...4&postcount=85

The link is from a post comparing the scores from an R290 (non X) with 290X flashed bios vs 7950 Stock CF vs Titan, with same OC level...

Some info from the page 6
**UPDATE**

Hynix and Elpida are both just as good as each other.

I took my Elpida card which could only do 5700MHz, flashed the Asus BIOS to it, pumped up the voltage and now the Elpida card is matching with 6600MHz.

So there you go, Elpida, Hynix, it don't matter. What matters is voltage control.

Asus BIOS FTW.

By the way this is an R290 I've flashed with R290X BIOS, works a tread, but shaders not unlocked, but can now hit 1220 core and 6600 RAM on the regular R290 as well. At these speeds this also obliverates Titan. Incredible value!
What we have noticed though, flashing the X BIOS to none X does seem to reduce motherboard compatibility. Using stock BIOS it will boot in any motherboard, using the Asus flashed BIOS it will only boot in Asus motherboard.

Maybe because its an X BIOS and some boards are showing a fault due to shader count not being correct. Soon we will get an Asus none X BIOS, when we do, we shall see if that fixes the in-compatibility issues.

Still its nothing major as you can't go wrong due to the dual BIOS nature of the card.

Facts are you can flash the cards, get voltage control on both X and none X. Things will only improve.
Stock air cooler.