I'm currently using a small Hanna stir plate, making large staters is pushing this stir plate to the limit. Looks funny seeing a 5000ml flask on it. I was searching around and found this stir plate (The Black Maxx, by Tower Cooler.com) it's so big you can put a 5 gal carboy on it and get a good vortex. It's expensive, but if you want the best this is the one. There's a U-tube video on this, check it out.