Just installed a Kraken G10 to my reference 290 with a H75 after having it make a ton of coil whine noise and very strange artifacting showing up on screen when switching in/out of games or removing/installing drivers (which I ruled down to the 94 degree constant temps under load)

And all was going well for a while, 30 degrees idle temps and 50-55 under load, but after around 15 minutes of a game running my PC shut itself down and rebooted. After that I can't get any signal from the GPU at all.

VRM temps were fine (70 under load)
I have the G10 fan plugged into the GPU with an adapter at (at 100% in afterburner) and the cooler fans plugged into a 2 to 1 adapter which goes into my Sys_1 fan on my motherboard (Gigabyte Z77-D3H)

I'm pretty sure that the card is dead but if anyone has any ideas I'd appreciate it.

If I was in your position (and I was a while back with a 7970 and an Accelero Hybrid I), I would take the Kraken off, check that the core isn't physically damaged especially on the corners, and put the original cooler back on. If the card still works either thank your lucky stars and use the card with the original cooler on, or try putting the Kraken back on if you're brave enough now you know the card is capable of working.

Just tried with the old cooler, still nothing unfortunately.

I guess I can just use the H75 for my CPU and get a new graphics card, what is the best right now for around £250?

Grab a second hand 290, the new Corsair HG10 looks good, much better than the G10.

Would it not be worth getting something like one of these?

http://www.overclockers.co.uk/showproduct.php?prodid=GX-273-MS

http://www.overclockers.co.uk/showproduct.php?prodid=GX-013-PL&groupid=701&catid=1914&subcat=1010