Tower-style CPU HSFs and passive chipsets?

[A Shiny Demon]

I have the Asus A8N32-SLI Deluxe motherboard, with the passively-cooled, heatpiped northbridge and southbridge terminating in a heatsink just to the left of the CPU socket. With the stock 939 HSF, the northbridge idles at 35C. I'm in desperate need of a new HSF, especially since this is my first summer since I've ventured into the land of overclocking and it's killing me on CPU temps and max OC. I want to know if a tower-style cooler (I'm looking at the Thermalright Ultra-120 or ZEROtherm BTF90 "Butterfly" in this category) would endanger my chipset due to lack of airflow. My choices for HSFs with the fan blowing down on the board would be the Thermalright SI-128, or I might wait for the Zalman CNPS8700, though I can't really find any information on it in English. I have two 120mm case fans, one intake and one exhaust. The rest of the system is in my sig, though I doubt it matters.

Any input is appreciated. Thank you!

 

[A Shiny Demon]

Please?