Is 400l/hr pump adequate suited to dual rad 120?

That is a very high flow pump, so it will do fine.
My water pump is 90l/minute...
and it works fine...

I think it more depends on the pressure the pump can produce as the more items in your water cooling system i.e. rads, water blocks and so on, the higher resistance with water flow. The thermaltake bigwater 745 runs through two rads on a 400 L/P pump so you should be ok.

lol, i was thinking more along the lines of head pressure.... but i guess brand does matter... a bit haha