Tvheadend

Hi.
I need to stream and transcode 16 DVB MUX/channels in the same time with Tvheadend and I need to make a server which is able to do this job without problems.
I saw the Supermicro X11SSV-M4 Motherboard (https://www.supermicro.com/products/motherboard/Xeon/C236_C232/X11SSV-M4.cfm) which I read that is capable to stream 15 HD channels in the same time, but it's a Mini-ITX motherboard and I need to mount it into a rack.

Could you advise me any other hardware configuration to make this job? Could you make me an idea of what kind of CPU and how many RAM amount I will need?

Thank you very much!
Bye