Home Entertainment. We are planning on purchasing a new big screen t.v. and I'm sure I should get

Question

We are planning on purchasing a new big screen t.v. and I'm sure I should get a new sound system at the same time. I have an older Sherwood RV-5030R amp. and it says in the manual it has Dolby 3 Stereo and Dolby Pro-Logic Surround. I also have a Mission 70ASA powered subwoffer. Should I use either of these units? I know nothing about sound systems.