Ah, so it's just a HOB?
Before you add anything else, I would get that extra live rock (yes, about 8lbs) and add a decent powerhead (Hydor Koralia or just something like a Maxijet) to get some good flow over the rock.
If you cant or don't want that much rock in the tank, add at least a little bit more and get a big canister filter.
As it it, your tank has a little bit too much potential for things to go wrong IMO. High fish load, low flow (and very poor circulation because its a HOB, the outflow is next to the inflow) and only a small amount of live rock.
Sort the filtration out then you can concentrate more on your stocking. I personally wouldn't have that many damsels in a small tank anyway.