Monks end up being the most powerful of all the classes, IMHO. At high levels, it got boring walking through rooms of hostiles and pounding everything without fear of going wrong. Monks are worth it, but I didn't find them that challenging, after a while. There are other threads that talk about this, if you want to search.
I don't want to discourage you, cuz Monks really do rock. Just too much, maybe, at high levels. I was Lawful Good and had Keldorn (a must!), Minsc, Aerie, Jaheira (untill I found Imoen), and Nalia. Heep Imoen and ditch Jaheira. You won't need the extra fighter power in Jaheira and Aerie is enough of a cleric at high levels. Plus, you can really use the firepower of three mages. Entire party is good aligned, once Jaheira is gone.
Matti Il-Amin, Paladin, comedian, and expert adventurer. Proudly bearing the colors of the [url="http://www.svelmoe.dk/blade/index.htm"]Blades of the Banshee[/url]