Dell Precision 3620, maximum RAM speed supported

Hello there folks,

I have a question concerning the RAM of a DELL Precision 3620 or RAM Speed effects in general.

What is the maximum speed of RAM supported for a DELL 3620 precision?

I have an DELL precision 3620.

i7-6700 processor

Gpu geforce 1060

Is a DDR4 -3200 MHz supported?

Preinstalled is 16gb ddr4 2166 MHz.

Does a full exchange (buy new 32gb @ 3200 mhz) make sense for a Performance boost or is it so low that i should just buy another 16gb 2166 MHz and its fine with 32 gb mhz 2166.

Maybe its not worth spending extra 75 Euro for 5% Performance boost compared 2166 vs 3200 ddr4.

Thanks!