I would do both GAC and GFO, I wouldn't bother with either the UV or ozone. As far as the Ca reactor is concerned, given the size of your tank, you might be better off with a two part doser. Either way, you won't really be needing either method for a while. Also, I'm a proponent of bio-pellets, which you also might consider. I have all my reactor's on their own pumps, so I didn't do any plumbing for them.