Dear lucianp.
Since you are using a scanner with a diffuse light source, like the Elite 5400 II, you already made a good choice for b&W
negatives, which still contain silver halogenide. Other thn that you might want to make sure that you will be scanning with no less than 2700dpi in order to cope with the kind of potential a well exposed b&W negative (shot from a tripod) can give you and in order to maintain the authentic grain of the film.
Tests have shown that SilverFast considerably increases the dmax of this particular scanner by our multisampling with auto-alignment. No I can not tell you how much the damx was increased because this info is part of a publication being released in August, sorry. I would like to point you towards a tutoriaal from Ian Lyons on the Auto-Adjustments which needs to be tweaked a little for b&w negs
http://www.computer-darkroom.com/sf5-negafix/edit_2.htm
Best,
JAN