The optional D-Star board goes for around $200.00, now that's not to say your
IC-91A is only worth $150.00, but I would tend to think it not worth too much more without the D-Star, and no box or manual. The Diamond SRH77CA antenna should add approx $30.00 to it's value.
The main issue with the 91's is the fact that they get real hot when transmitting on high power, it's the same complaint I hear from everyone who owns that radio, that and Icom does not offer a GPS speaker-mic for that model.