Hmmm... I'm in the same situation. We've just been offered a gig this Saturday after another band cancelled, and it's quite perfect because it's relatively small and informal, so a great chance to check out if the set list works before some more important gigs later - but our bass player just wrote back that he couldn't make it (no specific reason given) and he didn't feel he would ready anyway. :-/
He's now THIS >< close to getting kicked out of the band...
So, I'll try the split signal -> eq -> octaver thing and see if it works - might have some experience to share with you afterwards!