Is it just my bad memory, or in the original version did the original music swell just as Obi-wan is closing his eyes and putting his saber up? (before Vader delivers the slo mo killing blow) Or is it during his grin as he's glancing back at Luke?
If so, that would be more poigniant than the "climax" of the prequel music followed by the music coming in during the slow mo of the clothing falling.