I just bought a house that came with a DSC PC1550 security system. I understand the system is about 20 years old now so I'm wondering what to do with it. I'd like something that that gives me remote access via my smart phone and gives me the option to add cameras if I want in the future. Can I upgrade just the main panel and leave the keypads & sensors where they are? Or am I better off ripping everything out and getting a completely new system? Thanks.