Now I'm still learning so this may sound like a dumb question but in this list, how do you know what your power requirements are needing to be if you don't have your equipment set already? Have you already designed the system and you are now just tackling the electrical first?
Number uno if your going to scrimp on a system NEVER NEVER do it on electrical! If you think you have enough try and double it. Even with smaller systems the minimum electrical you should plan on is a HO alt 200 amps or better and 1-2 batteries.