I would strongly recommend you find a reputable local audio production company to come take a look at your room, budget, etc. and make suitable recommendations and help with your install and setup. It's very easy to waste money on gear that might not be right for your application, and it's also easy to damage your new gear if you don't know how to use it properly. There's more involved in a full room multi-speaker setup than some speakers and a mixer. You also need one or more speaker controllers (which need professional setup due to EQ and delay requirements), appropriate wiring, etc. There are also major differences between DJ mixers and real audio mixers and you'll want pro advice on which would work better for you.
At the least, if you can't find a good local audio production company to help you, contact pro music stores like Guitar Center, Sam Ash etc., and ask for their help. I'd be happy to offer you my company's services except we're located in PA, not exactly convenient.