Noisy Optiplex 7020

I bought an Optiplex 7020 last year to use as a HTPC. It was a good fit with one exception, it was a bit noisy. I was going to tackle it, but got busy and forgot about it. I'd like to get back to it. I re-pasted the CPU. The main source of the noise is the two fans. Of the two, it seemed like the front case fan was the more noisy, so I unplugged it figuring the CPU fan was more important. It seemed to help, but I noticed when the temps rise above 50°C, the fan seems to find another gear. This cranks up the speed and therefore the noise. I'm wondering if I replace one or both of the fans, is it going to help?   I'm also wondering how quiet I can reasonably expect to get this?

My last HTPC I built was whisper quiet, though you could control the fan speed in the BIOS. I did not see this option of my 7020. My Optiplex 7010 desktop is more quiet too. I like the 7020 and would like to keep it, but want to get the fan quieted down. Thanks for any help.