somebody mentioned putting 'Duel of the fates' into the Luke/Vader light saber battle at the end, but to be honest I think the light saber battle in Empire is the most gripping and closest to perfect battle that we see in the entire saga, it's a clear cut battle of the minds and a game of cat and mouse rather than the over the top aerobatics of the prequal trilogy, apart from some tweaking of the light sabers and a few effects shots, I think it would be best left pretty much exactly as it appeared in the original.