I have a Sapphire 7979OC and think it's a pretty good card. Has a custom dual fan cooler, dual bios and black PCB. It also has a dual-link DVI port which some 7970's do not have, meaning you'd need to buy an active adaptor if you planned on using it with a monitor with higher than 1900x1200 resolution (or alternatively use the HDMI port, but my monitor does not have HDMI).
It's reasonably quiet, I can hear a small amount of fan noise when it's heavily stressed, but nothing annoying. That being said, I run it at 1150Mhz, so extra heat will be generated there. In terms of overclocking, it hits 1200Mhz fine, with a small voltage increase (can't remember what of the top of my head), and may even go higher, I've just not yet tried.
For complete silence, you could always go the water-cooling route. This is what I plan to do, as I already have a loop installed cooling my CPU. I also think black PCB's look better with waterblocks - lame, but looks do matter.
Performance-wise, I don't go on synthetics, but it maxes out BF3 at 2560x1440 with a minimum of about 50FPS. Same with Max Payne 3. That's good enough for me.
There are many decent 7970's with custom coolers, but the combination of features on the Sapphire 7970OC is why I can recommend it.