DURING A NIGHTTIME ARR; A320 FLT CREW EXPERIENCES GPWS TERRAIN ALERT WHEN CLRED DIRECT TO LAS; DSND TO 6500 FT MSL FROM OVER LUXOR INTXN.

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WE WERE ON THE GRNPA ARR TO LAS AT 12000 FT OVER LUXOR INTXN WHEN ATC GAVE US A CLRNC DIRECT TO LAS VOR EXPECT RWY 19R. THEN WE WERE GIVEN A CLRNC TO 6500 FT. I STARTED THE DSCNT. THE FO AND I AGREED IT WAS ODD TO BE GIVEN A CLRNC TO 6500 FT THAT FAR OUT. I SLOWED THE DSCNT TO 500 FPM AND WE WERE GOING TO ASK ATC TO VERIFY THE ALT CLRNC. AT THIS TIME; WE WERE APPROX 33 MI OUT APCHING 7000 FT. BTWN 7000 FT AND 6700 FT WE GOT THE GPWS ('TERRAIN; PULL UP') WARNING. I IMMEDIATELY WENT TO TOGA AND PULLED BACK ON THE STICK TO CLB. THE FO ADVISED ATC THAT WE HAD A GPWS AND WERE CLBING. ATC RESPONDED THAT THE MVA WAS 6400 FT FOR THAT AREA. WE ASKED FOR A NEW ALT AND WERE GIVEN 6500 FT WHEN ABLE AND A HDG OF 250 DEGS. AFTER LOOKING AT THE 10-1 CHART; I SAW THE HIGH TERRAIN AT 5363 FT SO THE 6400 MVA SEEMED ACCURATE. SUGGESTIONS: I REALIZE THIS SUBJECT HAS BEEN ADDRESSED BEFORE; HOWEVER; I BELIEVE LAS ATC SHOULD BE NOTIFIED THAT WHEN DSNDING US THAT FAR OUT; IT COULD GIVE US A GPWS. ALSO; IT WAS BELOW THE CLASS B AIRSPACE. AND; I WILL REQUEST TO STOP AT A HIGHER ALT IF I'M PUT IN A SIMILAR SITUATION.