They come with 20 tooth pulleys for all the motors and I think for the lead screws as well.
I switched my X and Y motor pulleys to 16 tooth ones quite some time ago and the lead screw pulleys to 40 toothed ones.
I am very happy with the resulting improvements in resolution and smoothness and feel no need for 0.9 degree motors on any axis.
I still have the pancake motor I ordered for the Titan sitting in my tool box but just haven't gotten around to installing it (way too busy with other things lately).
But I'll get to it one of these days. 
Here are links for both the 16 and 40 tooth pulleys-
16 tooth, 5mm bore-
40 tooth, 8mm bore-
You don't need to change the motor pulley on the Z axis, only the lead screw pulleys (40 tooth).
So you only need two 40 tooth 8mm bore pulleys (Z) and three 16 tooth 5mm bore pulleys (X and Y).
This is a very inexpensive and effective upgrade and if you can do it from the start as you are building the machine it is super easy to do.
I hope this helps you.
