I have the xp120 and it cool GREAT, the si, though it fundamentally shouldn't does cool just almost exctly the same, the si does have much better motherboard compatability I personally cannot speak to the fitiment of either. According to thermalright's compatability list, on that particular motherboard there will be slight contact between the heatsink and other components on the board, this will not however negatively affect the performance of the heatsink or the motherboard, the si-120 does not contact at all and should fit perfectly. Have you considered the ultra-120 or other tower style heatsinks?