CFM = noise.
Most CPU coolers use something like 30CFM 80mm fans, so you can see that you've got a real screamer there. My hunch is that it normally runs at 20-25 CFM. IF 40-60 CFM doesn't cool it, nothing will. With sustained 100% CPU loads, it might get up to 40-50 CFM, you'd be the best judge of that. It's really a matter of how much noise you're willing to put up with. 80 CFM will be so loud you can't hear the TV in the next room.
My experience has been that Panaflo fans are WAY quieter than the others, even with equal CFM ratings. Most of them have a growl or whine type bearing noise, Panaflo has none of that.
You won't hurt anything, if the CPU gets too hot it'll shut down. (but it wont get too hot)
But I'd still take a stab at getting a replacement from Dell.
THIS might be my choice for over-all quietness with adequate CFM capability. Give the low cost, I'd get both and see which gives the least noise and best cooling. (CPU temp)