i found a review where the hyper 48 was tested against the Swiftech MCX775-V which beats the xp 120, and it got very close scores also as u can read here the comparison of the Swiftech MCX775-V and the Hyper 48

http://www.insanetek.com/index.php?page=cmhyper48


and the review of the Swiftech MCX775-V vs xp 120 and other competitors and u will see how well the xp 48 can compete with these heatsinks:

http://hi-techreviews.com/nuke/mcx775/mc775_Page1.htm