I'm not qualified to answer your specific integration question. However, back in the day, I was a computer nerd that got into pushing my PCs as fast as possible while focusing on cooling as quietly as possible - specifically home-brewed water cooling. I had a huge bin of cooling bits and bobs including fans and after testing lots of different fans, I definitely found my favorite: Panaflo fans by Panasonic. It's their "hydro bearings" that make these so quiet vs ball bearings (less whining). They come in a few speeds, ultra, high, medium, and low indicated by the last letter in their part number. Example: FBA12G12L <--this is a 12v, 120mm fan, running at low speed.
I doubt that static pressure is that important in your situation, because it looks the heat sinks have plenty of space between fins (less to hold back the flow of air). Air flow is probably the most important factor - more air, means more cooling, but also, usually, more noise. The fan with the part number quoted above produces ~70CFM at only 30dB which is virtually silent. You'll still have to work around the problem of being only 12v, but if I had your project, that's where I would start.
