I've got to admit that, and it isn't often you will hear me say this, I think an ad is a good idea. Seeing as interest in the band isn't at its greatest (though I have noticed it has increased in the past year or so) I don't think new visitors would mind it that much.
I would have thought that later in the year as more dates may be announced then forum traffic will go up and the cost seems to be linked to number of views.