The Volcano 7 and 7+ are very good. I currently use a Volcano 7+ to cool my P4 1.6A and a Volcano 7 to cool my T-bird 1.33GHZ and my g/f's XP2000+. The heatsink on these coolers is first rate. However, these hsf's are rather loud, mostly due to the high rpm fan that usually comes on them. BUT, for your application the Volcano 7 is easily modded to make it STEALTH. The Volcano 7 uses a standard size case fan, which means that all you need to do is find a quiet case fan that blows a lot of air if you wanna make it quieter. At my local comp show, they had some (I forget the name) clear case fans with blue LED's inside the hub. These spin at about 2800 rpm and are really really quiet. They also create a significant airflow (about the same as the stock volcano fan). So I took the heatsink apart and changed the fans, and the XP2000+ still runs at the same temp. Plus, now the heatsink looks cool through the case window because the fan is clear and the "Tt" cutout on the fan cover on the heatsink lights up BRIGHT BLUE!
Another good substitute would be the Cooler Master fans because they are quiet and come with a speed adjustment potentiometer so you can control how loud it is. With a combination of this heatsink and a quiet fan, you should be able to make something that cools very well and is no louder than your other case fans/video card fan.