I was looking at getting a denon pma-600 to connect my TV and 4k player. I've got some small mission cube speakers and a sub. I was going to go down 3.1 channel but I'm not sure if the extra centre speaker will be benificial, hence was looking at a stereo amp with optical and sub option. Will i get issues with lyp sync issues when using tv/4k? Or am I better off getting a cheap av amp?