The A unit will require soldering the headlight to the board. The Digitrax have really small soldering pads and the headlight don't dim very much if you plan on using Rule 17 lighting.
Just be aware that BEMF and advanced consisting don't work good together. But the old style consisting works fine with BEMF and I love the switching speed function Digitrax uses.
Gary
Here are the Digitrax links:
http://www.digitrax.com/prd_mobdec_dn163i1a.php
http://www.digitrax.com/prd_mobdec_dn163i1b.php
Be grateful your first "victims" has drop ins and doesn't require hard-wired decoders.
Best!