You could get just a receiver and speakers but it will probably cost more than buying what is commonly called a Home Theater in a Box. Those are usually much more compact units with the speaker and sub woofer, the "player" which also acts as your receiver. Your Blu-ray player cannot act as the receiver for the speakers. All it can do is play movies.
But since you have the Blu-ray player, you could get one with just an up converting DVD player and save some bucks on that end. And DVD players (and Blu-ray players) also play music CD's.