Are you using any of the digital outs (optical or coax) on the Sony? Or are you using the analog outs on the player?
If you intend to use the digital outs on the new player, it will not sound any different than the Sony. Analogs on the other hand, for a much better player, might make a difference.
That said, actually perceiving this improvement depends on how well the room's acoustics have been controled. In all but the most well thought out, dedicated listening spaces, the room's effect will drown out any sound improvement from the electronics.