DVD Upconverters???

Question

Okay I have a Magnovox HDTV 1080i tv with no hdmi hookups. It just has the hdtv component hookups. They look great with the cable hd channels and the xbox, but i was wondering if i would benefit from the up converters.i bought one a couple months ago and returned it because my Tv detected it as still being 420p. so my question is... does the up converters have to use the HDMI cable to look better or are they still better than the progressive scan dvd player i have now??