My dad had a very similar Fujitsu panel. I see you mention that you don't notice much difference between this set's performance and the new sets in stores. I'm pretty confident that if you had to bring one of the newer sets home the difference will be quite apparent. Something else to consider is that your current plasma is not full SD resolution either, so you're missing detail on even standard definition material.
My dad upgraded from his Fjitsu to the previously mentioned Samsung panel, he was very happy with the result.