Soldato
Personally I couldn't pick between 5-10 as I enjoyed them all as much as the other.
I'd love that music as an mp3 .
I actually thought 10 had the best soundtrack.
There was nothing memorable about it though. The boss battle music was pretty damn good but that's all I can remember.
(on a side note, X is the only FF other than VII that made me bawl like a baby, pity X-2 ruined the ending and threw it away by having Tidus actually come back)