Hey there, I have the AR620-T which is the taller version and another 40 litres (130) My tank was origonally purcahsed for the use or tropical freshwater with the assurance that if I decided to goto marine everything would be ok. Turns out its an absolute nitemare. It has no support to use a protien skimmer, or a sump for that matter if you wanted to go hardcore into marine.
I had to change my lights to blue's, so the factory light tubes are useless for marine tropical fishes. However, if you are prepared to do regular water changes i.e. 5-10% per week and have access to NSW then go for it as this is going to be the way I'm going to do it. I will plumb in a protein skimmer on the right hand side of the trickle filter making things a little better.
My tank is still in cycle at the moment, (6 weeks) and once my ammonia levels drop I will add fish and see how this goes. If the system packs up and deems unsuitable to sustain marine tropical I will most likely go cold marine and support local fish available from our habour, crays, mussels e.t.c.
Good luck with it, but if you can stay away from the AR's as they truely are not suitable for marine, although your petshop will say so lol.