Well sorry to say but they have put you wrong, all of those fish in only a 120L tank isn't really good for them and I'm sure everyone would agree with me on that.
It will be good to finally have some more all in 1 tanks to choose from instead of just the RSM, if you look in America they have sooooo many different all in one systems.
Heres what I think:
1.Metal Halide option
2.Auto Top Off option
3.Chiller
4.Better Skimmer
5.Better quality timer
6.wave option on the pumps (as I have seen on the new JBJ tanks)
well what I have just tried doing and it worked was fit a 250w with and external ballast but I didn't fit a piece that special glass cause I haven't got any.