Calcium/Alk: No need for a Calcium Reactor for a Soft Coral tank. There demands arent even close to an SPS reef and it isnt cost efficient to run one. The negitave effects of reactors such as low PH arent worth the trouble on a soft tank. I would suggest a 2 part additive or top off of kalk. Randys DIY 2 part additive is dirt cheap so you might want to look into that.
Flow: No need for Steams, Waveboxes, huge return pumps on super hightech closed loops ... 3 PowerHeads on a wavemaker will work fine or if you dont like the look of that a small closed loop on a SCWD will do just fine. I am using 4 Modified MJ900's on a Red Sea Wavemaster in a 120.
Light: Depending on the tank dimensions you could use anywere from PC's to MH's. The light demand is considerably less and will be nothing compared to an SPS tank. I run 2 150w MH's and 2 65w PC Actinics. I would have gone with 4 54w T-5's if I didnt want to keep Clams and Anemones.
Filtration: I would not suggest heavy skimming as alot of soft corals seem to do better without large skimmers or atleast there is no need for a big skimmer, there are actualy several soft tanks that run completly skimmerless. I would run phos media becuase it tends to have negative effects on the corals. Denitrators are fine but not needed even with a high bioload. UV is not nessasary and would kill benificial plankton that soft corals feed on. Ozone is fine and would be nice way to have a super clear tank. I would run a small skimmer in combination w/ a refugium and use a decent amount of carbon.
Substrate: I'm not sure if your a BB reefer but I dont think BB is the greatest thing for soft coral tanks. I think a sand bed has alot of positive effects on soft corals and even if "old tank syndrome" occurs I think it would be worth the hassle to remove and replace the sandbed.
Soft coral tanks can be as simple or as complicated as you want ... you could run a perfectly healthy 55 with just a hang on skimmer, a few PH's, DSB, 2 part additive and keep up w/ water changes.
If you have any other questions just ask,
Good luck