Home Cinema upscaling

I'm new to posting so forgive me if I'm not doing it correctly. I have a Panasonic SC-HT900 Home Cinema and Panasonic Viera TH-37PX60 Plasma TV. Picture quality is excellent through Sky HD but can I improve the dvd picture by either buying a DVD Player (preferably Panasonic) with HDMI output and can this be connected to my Home Cinema to give Dolby Digital surround sound as I get at present/
Alternatively would I be better buying a new Home Cinema with HDMI output and selling the SC-HT900?