From various reviews I've read, the upconverting players seem to show the most improvement on fixed pixel displays (plasma, DLP, LCP etc). Not familiar with your Hitachi's numbers, but if it's a RP/CRT, then I doubt you're going to notice a big difference. But heck---you've got the player so why not give it a try? If it doesn't look like the difference is worth it, you can take the cable back for a refund and hook the component cables back up.
Mort