Optimize setup for rear-projection tv

Looking to optimize the setup for the following;

52" RCA rear-projection tv (model P52960)
Rogers Explorer8300HD PVR box

i currently have it connected via a component cable
PVR box has a HDMI output, tv doesn't have an HDMI input

tv has 900 vertical lines, and pvr currenlty shows 480i
what is the setup to have the tv at 780i (or higher if possible)? Will a HDMI-to-component cable increase the picture quality?