hi mark, your setup is looking great!
in relation to your last question, i have a large tank also, with 2 fx5s and another 1000ltr/hour can - i also have two 300w heaters. when i do a water change, i use a water hose from the garden, i remove the one way valve in the bit that clips onto the outside tap. i will put the hose in my tank, sort of half way down, then i will turn the outside tap on....this primes the whole hose, i then pull the hose from the tap and allow it to backflow out....when i get it down to the level i want, i then reconnect the hose and fill it up.
the temp will go down, but ive still got a lot of water already in the tank, plus the two 300w heaters kick in - ive never had a problem, so if your thinking of doing the same, try a bit at a time to see how the fish react, keep doing that until you get around how much you want to remove each time.
watch out for some hoses, which have a white powder in them to keep them bendy....mine doesnt have any powder...but doing it this way saves
on keep rushing back and fourth with buckets!