Alienware Aurora (Late 2009) GPU Upgrade Problem

Hello,

I have purchased a brand new AMD Sapphire 290 Tri-X OC, and upon installation of the card I have encountered a boot error. It's worth noting that this is a UEFI GPU - I don't know much about that that means other than it is a new BIOS type. 

Upon power-up, it has a repeated 6 Beeps (points to a video card problem) until the power button is pressed again. Fans spin on the GPU - black screen & no boot.

I have the standard 875w PSU - so that shouldn't be an issue?

It hasn't booted at all, but when I put the old GPU back it boots perfectly fine.

I purchased this Alienware Aurora new from Dell in Nov. 2010 - so I am confused as to why I have (according to the Dell product checker) a 'Late 2009' model - as opposed to the R2/R3 I should have gotten?

Anyway - I am baffled as to why the computer will not boot - as the PSU & everything else is sufficient to my understanding.

Replacing the old ATI 5670 (it was in crossfire - but only stuck one of them back in) that came with it and the PC booted up no problem whatsoever. I then uninstalled AMD drivers and control centre entirely and rebooted. Still no luck.

Specs:

• i7 920
• 2x 4gb RAM (newly installed - but tested & working)
• 1x 250~gb SSD (newly installed - working for a couple months without issue)
• 1x 500gb HDD
• 875w PSU

If there are any other details I need to provide please let me know.

Thanks in advance for any help - it's much appreciated!