Lala Land Records, which have previously released the Mask of the Phantasm soundtrack, has released 2 CD’s of the original score of the animated series. The first volume is in a limited edition of 5000 units and the second volume has 3500 and I would expect them to sell out fast.
Lala Land are a great speciality soundtrack label and their releases usually have extensive liner notes and excellent artwork on their releases.
First volume: http://www.lalalandrecords.com/BTASV1.html
Second volume: http://www.lalalandrecords.com/BTASV2.html