I'm using the older stock AMD cooler now (that came with my 3800 X2), and the sound is good, cooling could be better. IF I replace it, I'll keep your review in mind. I was looking at the XP-90C, but now I'm not so sure.
VGA cooler roundup is next on my to do list; Arctic Cooling (2 units), Zalman (2 units), Titan (1 unit), Thermalright (1 unit) a new rather unknown party, 2 different stock coolings from 7800GT and maybe Thermaltake.
results out soon. (soon can be anywhere from 1-2 weeks, I'm doing these tests after hours)
I ran the xp-90 on my non OC'ed x2 4400 for a little while with the recommended Panaflo fan (at all different voltages). My experience was the stock cooler (the first heatpiped cooler for the x2's) performed better than the xp-90.
[rant]I've never understood the attraction of ThermalRight sinks since the SLK days. I see reviews, people going on and on about them on forums. The sinks I've tried of theirs, I've always found them to be inferior to other products available. I guess maybe you need a Delta on their sinks along with an array of Delta case fans, I don't know.[/rant]
Now I'm using a Ninja with a Nexus 120mm fan at 5v. Running cool and silent is beautiful.