I did a similar but,maybe,more radical mode of same chassis.
however it may not work for everyone or every use case.
my 846 was "A" model with dual Opteron, and quite old,
most noise came from fanwal but PSUs were like screaming banshees as well. non of those platinum or better jobs
.
since it was for my home needs and I do not expect a overly heavy load on the system I went at it with a hatchet
.
I took out the PSUs and supporting hardware, took out the fanwall and CPU fans and coolers.
I put in a regular, Silver 80 ATX PSU
replace 2 80mm fans on the back wall with quiet ones from the nearest Microcenter. cheap too.
replaced the CPU coolers/fans with a Cooler Master Hyper 212 EVO cooler. the only thing I do not remember if it was the 212 EVO ot T4 model. they look very similar and both use 120mm fans, but one is 1/8" toller and do not fit in the case. I think I used the T4 after all.
and for fan wall I string 3x1400mm fans covered with 1/2" hardware mesh on both sides, with zip ties.
it works and works well.
again my use needs are modest so for a high performance server this may not be optimal.