Wavemakers - The SeaSwirl is just a swiveling return outlet that directs current to different places in your tank. Great product, but it doesn't do anything by itself - you need to have it plumbed into your return line from your sump, or have it plumbed into it's own pump. The Koralia on the otherhand is actually a powerhead that is controlled to vary the output flow. It doesn't swivel, but by varying the output, you can simulate waves and such.
Reactors - I don't use one. Assuming you mean a calcium reactor, unless you have a huge amount of calcium hogging corals, in my opinion you don't need one.
Litermeter - all depends on if you're going to be dosing anything in your tank. Only thing it does is supply small quantites of liquid to your tank, normally on a timed basis. Can be used for fresh water top offs, adding calcium (kalk
), or water ever else you dream up.
Waste Collector - what you linked to is only for that one specific brand and type of protein skimmer. It will only do you any good if you have that brand/type. Many skimmers come with some option to deal with the potential overflow situation if you don't empty your skimmer cup. And some are designed so that an overflow doesn't happen - it just overflows back into your tank. And some skimmers will overflow for no good reason at all because they're just hunks of junk! I guess the lesson here is... just research skimmers before you buy, and get one that doesn't have known problems!