Sign up for the marine depot newsletter. They email you when they have sales. The nice thing is that most of the bigger stores will match prices, so if you have a preferred place (I love aquacave, marine depot, drs foster and smith, and BRS) they'll probably match any price you find.
"What, exactly, is the internet? Basically it is a global network exchanging digitized data in such a way that any computer, anywhere, that is equipped with a device called a 'modem', can make a noise like a duck choking on a kazoo." - Dave Barry