I particularly enjoyed the Kara no Kyoukai OST myself. :)
As for favourite Kalafina songs... 'Serenato', 'Oblivious', 'Mata Kaze ga Tsuyoku Natta', 'Ashita no Keshiki', 'Sprinter', 'Red Moon', 'Progressive', 'Kugatsu', 'magnolia', 'Alleluia', 'consolation', 'Mirai', 'to the beginning', 'Manten', 'ring your bell', 'Misundehiraku' and finally 'Believe' are the tracks I love the most.
Thanks for the warm welcome. :)