I have the Sapphire Tri-X R290.
It is shockingly quiet, the most silent card I've ever had or even heard overall from all cards I've heard(from friends, relatives, random strangers on LAN parties).
It has a Hynix memory and an ASIC score of slightly over 80%, but I haven't tried to overclock it yet simply because I'm on a 500 Watt PSU and while I've seen that people have gotten decent overclocks if they have a really good PSU, for those of us who are at the threshold of an acceptable PSU, I'd rather not try.
Also, frankly, I haven't felt I have even needed to OC the card yet. I'm running everything on ultra and I am getting really good fps. I'm less sensitive to maximum fps than I am to minimum fps. I'm seeing a very good and smooth experience and there's zero throttling as IEC previously pointed out.
The card is also running at very low temperatures. I'm getting sub-70 Celsius on demanding games. The most demanding is still mostly sub-75. That's pretty amazing.
I paid the U.S dollar equivalent of 430 dollars, when you strip out the shockingly high VAT and import tax that affects all electronics goods here in Sweden. That's about 20-30 dollars higher than the MSRP for the stock 290 with the notoriously lousy cooler.
I can recommend the card with zero ambivalency. I would, add, however that the card is quite long. So make sure you know that you'll fit it in your PC beforehand. There have been a few cases of people buying the card and then finding out they can't fit it in their cases, which is clumsy and embarrassing.