For your kalk stirrer I would be leaning towards Deltec. GEO makes good calcium reactors but overpriced IMO but as for kalk reactor it utlizes a power head to mix the solution which mean you can't or shouldn't dose right after the the pump has been on. I know the deltec unit isn't the cheapest on the market... There is an alternative unit that you can get from Avast marine, it's not the best built quality but it get the job done and it will eliminate the chances of you over dose your tank with over saturated kalk solution.
I have an oceanic chiller that's in operation since 3 years ago, never any issues. If you can get away with house hold portable ac unit in the room then I would use that instead beacuse once that chiller kicks on it will cool the tank no doubt but where ever that chiller is situated, that particular room will turn into a sauna.
I think you should do a external coast to coast and use either herbie of bean animal style overflow to keep it nice and quite.
one more thing, WE WANT PICTURES!
