Noisy Optiplex 755 mini-tower?

I bought this machine thinking it'd be a quiet one. I found, though, that it's not really.  I switched out the video card for a passively cooled one, thinking that was the problem but apparently it's not since the noise remains.  I've also read here that the SFF Optiplex 755 are "nearly noiseless."  So, my question to those who have a mini-tower:  do you find the fan noise rather noticeable or not?  I figure if others say their 755 mini-tower is quiet then I can ask Dell support about mine.  Alternatively -- perhaps someone has found a quieter replacement fan that works well and more quietly?