By all means buy the 6-gallon if you like headaches and constant frustration, and not being able to feed 600 at all, which is what you should be feeding if your bluegill are already big. If on the other hand you like machines that are dependable and well-designed, skip the barrel feeders, by Moultrie and Aquapro both, and skip Aquapro altogether as even their ADF-75 won't feed 600 unless it has been redesigned recently. I would tell you what I really think of the feeders mentioned above but that would require profanity.
I have the Moultrie Feedcaster, the "commercial-grade" feeder they make, running on one pond, and so far have had no problems with it, though another poster on here recently had the motor go out on his. At least it's a sensible design. You can buy one for what you're looking to spend, and while one feeder won't take care of every bluegill in the pond, I personally would rather have one smoothly-running, easy to fill and operate feeder running that allowed me to feed 600, than two or three that gave me constant problems, were poorly designed, didn't allow me to use 600, etc.
You can always buy one now and get a second one when you get the dough.
