If Rob Armstrong used ivory, that is quite a recomendation.
Brass make an immediately observable difference.
I have not tried beechwood but will now seek some out.
Ebony is bright but does not jangle like brass.
Quite a few people here in Kent are trying EZ-Pegs, which are brass but are also drilled so that the ball end sits behind, not in front of, the pin. I do not find them as enlivening as the cheapo JHS brass ones.

However, have you all made sure that your inner bridge plates are in good order? If the ball ends are sitting on a pile of squashed matchwood you will be losing the benefit of a hard contact point (and one of these years the ball end will pull right through). You can, if your inner bridge plate is not too chewed, get little brass plates with holes for the pins and grooves for the strings, to prevent further damage and to brovide a hard bearing surface. It takes a bit of rummaging on the internet to find them though.