However, the GT-5 is a better, more expensive unit. The reson for the numbering is that they released the GT-5, then decided to release a cheaper, "consumer" version, so they called it the GT-3 to make it sound lower. The GT-6 is the latest, but from what I hear it is different to both of them again, and isn't necessarily "better" than the GT-5, though "I might be wrong".