Add my vote for RGS 25 - good lines, matched domes, nice wood cab, "factory" spot plate, good looking mill.
I'm sorry if this sounds blasphemous, but as much I love them, and think they're cool engines, a K-28 is just plain wierd looking with that pump on its nose.
(now, to piss off Trent and Clark) - Leave it to Alco to design such a wierd looking mill.