the main bennefit from peat is the water holding capabilities.
compost is basically humus. humus is broke down material. most humus and compost has no npk. the best bennefits are the benneficial micro organisms, and the broke down elements and sometimes depending on compost alittle npk.

your best peat substitute is leaf mold compost.
mushroom compost is a compost made from mushrooms generally has alittle npk but not much
most manure you buy is going to be composted unless you get it from the source(the farm)

compost/humus, manure, topsoil, sand and or perlite is a good base. you want good water holding capabilitiess with good drainage/areation