PA1X Pro is a 76 key version with a factory fitted hard drive and is currently available for around $3000 the PA1X (not pro) is a 61 key version with speakers and no hard drive (which is optional or you can fit your own with any notebook drive I guess) and is not available yet PA1X is hope to be available by march, and that's it there is no more differences in them besides the 2 I mentioned.