All of your components will work in a freshwater set-up, except the protein skimmer. Skimmers will have no effect on your tank what-soever.
The only benefit might be that you will raise your O2 level a bit, but I think thats over-kill. Your lighting though top of the line is IMO to bright for cichlids.
Just a quick note on your current inhabitants, they have differing PH requirements for optimum health. The Oscar prefers softer water than your Jack or Living. Not a S. American expert, but I believe the Jack is a Central American and can tolerate higher PH range that the Livingstoni will need in order to prosper.
I think you will need to decide what type of TANK you are going to keep, a High PH, Neutral, or Acidic. You should test your water and see what comes out of the tap. It will make your life easier, but who said cichlidiots prefer the easy way
If you go with what come out of your tap, you won't need water purification, unless you have other issues with your tap water-I would test it for all parameters before you go buy anything too expensive.
Test it for PH, GH, KH, Nitrite, ammonia, Nitrate and maybe heavy metals.
If your going to spend a lot of $ on your set-up, spend a bit more and have your tap water analyzed proffesionally.
Go to fish stores and on the web and research fish that pique your interest, and will prosper under the conditions you can best provide.
I think you will get a lot of replies on this topic, hopefully a New World cichlid person will respond, specifically about your Jack.
Row well and live.
55g mixed Haps, mbuna, syn eup, Syn ?
125g mixed Haps, Labs, Syn multis, N. Ven, P. Phinoc, C. Moorii, Exo. anyg, Assorted Peacocks,accei, Red Emp