Used 7990 worth it for £190

Solution
Honestly, I personally wouldn't take one if they were giving it away for free. You may have different feelings, but it was discontinued after two months in production for a reason. Do your research before making this purchase in any event.

These are review quotes that tend to focus on the coil whine noise, but other issues commonly noted were a lack of frame pacing, Crossfire driver profiles, thermal throttling, and retail samples that underperformed their review counterparts:

"What is a major issue, though, is the extremely annoying coil whine the card emits as soon as it runs a 3D application... On the HD 7990, however, it is very apparent, and I don't understand how AMD missed such a glaring problem. I talked to five other...
Honestly, I personally wouldn't take one if they were giving it away for free. You may have different feelings, but it was discontinued after two months in production for a reason. Do your research before making this purchase in any event.

These are review quotes that tend to focus on the coil whine noise, but other issues commonly noted were a lack of frame pacing, Crossfire driver profiles, thermal throttling, and retail samples that underperformed their review counterparts:

"What is a major issue, though, is the extremely annoying coil whine the card emits as soon as it runs a 3D application... On the HD 7990, however, it is very apparent, and I don't understand how AMD missed such a glaring problem. I talked to five other reviewers and they all confirm it, so it's not an isolated issue. What makes the whine even more apparent is that it is constantly changing pitch and volume, drawing your attention to it by effectively overpowering the fans' "whoosh" sound."
http://www.techpowerup.com/reviews/AMD/HD_7990/31.html

"the high-pitched whine is noticeable enough to illicit raised eyebrows from observers correctly ascertaining that a graphics card shouldn’t be making those noises."
http://www.tomshardware.com/reviews/radeon-hd-7990-review-benchmark,3486-15.html

"When it launched, a generous eight-game bundle had me on the fence about the 7990’s prospects. But after spending time evaluating its thermals and acoustics (to say nothing about its crashes and performance hiccups in CrossFire, which could become a story unto itself), I can’t think of one reason to recommend 7990 to a friend. And, at the end of the day, that’s what this job is all about."
http://www.tomshardware.com/reviews/radeon-hd-7990-crossfire-overheat,3539-3.html

"Unfortunately, coil whine drove our sample’s acoustical profile into annoying levels. In applications where the HD 7990 displayed high framerates it wailed like a banshee and lower performance situations caused it to exhibit an odd “chugging” noise. This proved to be immensely distracting, regardless of how quiet its fans are."
http://www.hardwarecanucks.com/forum/hardware-canucks-reviews/60843-amd-hd-7990-review-malta-arrives-11.html
 
Solution