Help me decide what diode/module to put in my MX900 build.

Ok so it will be my first build and I bought the nice "Plug'n'Play" MX 900 from Rich (Lifetime17).

I would like to put in a nice 12mm diode+module from DTR.
But which one?
Help me choose a nice combo please.

I was thinking of a huge 7w NUBM44 450nm but I've already got two of Rick's units. :rolleyes:

I've also got some MX900 1.4W 520nm greens and 1W 638nm reds from Rick.

I was hoping for some input from you lovely people (experts) on my first build.

What would you suggest?
Something with a nice tight beam/spot/low divergence perhaps, either in a blue or a green?
Or maybe a more exotic blue (I can't really see much difference between the 450nm and 462nm (mind you it was a Sci-Fi unit so who knows what Eitan chucked in that one !
:horse:

So ok, what would you put in this nice unit from Rich?
What does DTR have in the 12mm that might be a nice addition to my MX900 collection?

Cheers
RB