Gigahurtz, it's funny that you recommend the XP-90 and XP-120, because right after I started this thread I started doing more HSF research and found those two to be very worthy candidates as well.
I had a Thermaltake Volcano 7 in my current system until recently. I'm not sure how it did as far as cooling but from Day 1 the thing was loud as hell. I mean it used to screech/whine every so often and it made me crazy. Finally, I just switched it out with the stock fan that came with my XP1800+ and my PC has been quiet ever since. So, I think I'll pass on the Thermaltake.
From what I've read so far, the XP-90 and the Zalman seem to be equivalent as far as cooling. I guess it depends on what fan you use with the XP-90 that will determine the noise level.
The XP-120 seems to be getting very high reviews. I am either going to get the new DFI UT Lan Party mobo or an MSI K8N Neo Platinum. So far, users are saying that the XP-120 does a great job of cooling.
Which 120mm fan are you going to use with your XP-120? If I do go with either the XP-90 or 120, choosing the right fan will be my next dilemna....
I hear Globe fans do a great job cooling and are very quiet. Not easy to find, though.