Is all that i need to make a stereo system an amp, speakers and a sub?

-I want to buy seperate things to make the speakers loud without spending so much for a big home theatre system, so is all i need , speakers, a sub, and an amp?A stereo system only has 2 speakers by definition; a two speaker system and sub is a 2.1 system'''you need a reciever like the Sherwood RX 4503 that has a sub output.... and speakers like the Dayton B652 (non Powered) and a sub....