Definitely go for a 500mW I have a labby running at 141mW right now and it seems like it would be fine for smaller shows as long as you have good fog. I haven't used any smoke or anything yet so I can't say how bright that'd be but the beam is visible is a well lit room.
no i got in to lasers because that are cool
i have already spent 600+ in the past 2 weeks..
i plan on creating a nice full color scanner eventualy, but i have to start somewhere