I had purchased the Rega Planet in 1999 and upgraded to the Jupiter in 2002. The improvement most notable for me was in the bass response which had more weight to it. There was also a slight increase in detail. The Jupiter still has the rega sound which is slightly warm and dark which, for many people is not necessarily a bad thing. Given that the changes were not that pronounced between the two players I'm not sure if upgrading to the Jupiter is the way to go. I would A/B other players in the $2500 - $3000 range like the Ayre, Moon, etc.. I would also recommend the idea of listening to the Musical Fidelity DAC A324(I think it goes for $1200) in conjunction with your Planet.
Good luck...
Good luck...