You don't mention your location, so make sure you know about any regulations governing your shows, especially if you move away from "private" functions.
Please keep in mind that the projectors you list DO present some potential hazards to your audience.
Regardless of your location, please DO NOT "audience scan" until you know how to take the proper precautions!
As colouredmirrorball mentioned, robustness and safety are EXTREMELY important, and please keep that in mind when shopping for an "inexpensive solution".
You might think about posting your location info on your profile -
you might find out you are in close proximity to some other experienced lasersist here on PL.
If so, you could probably get the chance to get some "hands-on" time with some equipment before buying, which could help with your purchase decision.
You already have a pretty good investment in projectors, so I wouldn't recommend "going cheap" on the controller, just to save money!
(I kind of equate that to buying some kick-ass speakers for my car, but powering them with an inexpensive, low-end radio)
Chances are, if you go cheap up front, you'll wind up buying again down the road.
RR
Metrologic HeNe 3.3mw Modulated laser, 2 Radio Shack motors, and a broken mirror.
1979.
Sweet.....