It doesn't hurt to look into EI, but I'm not sure if it's necessary. I'm no expert. What does your ped say?
Also, are you signing with them? Signing helps A LOT with language development, not to mention that it eliminates some of the frustration of figuring out what they want when they can sign it to you
There's a thread on baby signing if you're interested. I highly recommend signing (especially with the Signing Time DVDs).