Thanks, all!
I should have been more specific to help y'alls opinions. I have a NAS and HTPC that sit in basically a hidden space in between back to back rooms. The original owners built a closet in one room and then left an alcove between the closet and fireplace. I just covered up the alcove with shelves to match the rest of the room. There is a space that's about 20"(w) x 34"(d) x 8'(h) behind the shelves now that I use for storage.
I measured the temperature in the space over the year. In Summer, it gets to be 84F and in Winter, with the fireplace stoked, it gets to be about 78-80F. So it's basically a lack of insulation from the attic that shows the heat/cold temps.
So to my requirements, I'm looking for long term fans that will be able to manage heat and dust. Noise isn't a priority.
However, thanks for the other, more quiet fan ideas - I need them for my fun (games) PC which I guess I could call it my, "Top Gun Demo" rig. (That comes from the old Circuit City Audio/Visual selling points - pop in the tape/DVD of Top Gun to the catapult launch sequence and crank the audio up.) It's that loud.