You won't take the 20% hit for RDD itself, prestige classes do not count, you will, however lose it on the multiclass from monk to bard/sorc. The easy way around that is to be human, or, to keep the two standard classes within one lvl of eachother.
Edit: On the subject of that, in Icewind Dale 2 they had preferred classes, which would allow you to dual class without penalties, if your higher lvl class was the preferred one, I'm not sure if that applies here, or not. Enlighten me...
[ 06-12-2005, 12:06 PM: Message edited by: robertthebard ]