Sounds like something I would do. You have an awesome heatsink to begin with, but if you really want a higher flowing fan, a Delta would be a great fan, however I have had a hard time finding them also. There are a couple of alternatives:
<A HREF="http://www.coolerguys.com/840556017042.html" target="_new">http://www.coolerguys.com/840556017042.html</A>
<A HREF="http://www.frozencpu.com/cgi-bin/frozencpu/fan-10.html" target="_new">http://www.frozencpu.com/cgi-bin/frozencpu/fan-10.html</A>
That was one of the things I didn't like about my latest heatsink, Gigabyte 3D Cooler Pro.
My Desktop: <A HREF="http://Mr5oh.tripod.com/pc.html" target="_new">http://Mr5oh.tripod.com/pc.html</A>
Overclocking Results: <A HREF="http://Mr5oh.tripod.com/pc2.html" target="_new">http://Mr5oh.tripod.com/pc2.html</A>