Hardware Requirement

i want to use asterisk in my company but i don’t have any idea about the hardware requirement (CPU, RAM)do i need for my solution so would u please help me what is the requirement do u need to get a stable solution and here is my scenario:
1- 60 concurrent SIP/calls.
2- 100 voice mail.
3- 16 external lines (FXO).
4- 4 conference room with 4 parties capacities for each room.
please help me in that if you have any idea or any successful scenario.
thank you so much for being patient with me.

Any current dual processor server with 2+GB RAM will do fine for this.

With 16 FXO lines I would check to see if a partial T1 would be cheaper. In my area as soon as you get to about 8-10 lines the T1 becomes cheaper and can easily be expanded if necessary.