My understanding is that iTunes supports up to 20,000 tracks on 30Gb models, and 50,000 tracks for 60 and 80Gb models (Gen5 and Gen 5.5). Are you in need of even more than that? I know the Gen 6, 6.5, and 7 (120Gb) iPods only recognize up to 128Gb but will allow 50,000 tracks in that amount of space, and the Gen 7.5 (160Gb) will do 50,000 tracks but with no known limit on size, like the Gen 5 and 5.5. I use .wav files so my track count in 256Gb is around 6,000 tracks.