I'm using a 50W morimoto kit from TRS in my SMT with no issues after a month of commuting. I ordered mine over the phone and asked them about the 50W and they said, no problem. I'm surprised they steered you away from it.
I do recommend ditching the provided harness and making your own. Mine had two relays when only one was required. I added a time delay circuit so I can start the bike before it comes on.
The D2S projector pattern isn't superior to the H4 out of the box but with a nibbler along with the extra lumens, it can be.