"a chain is only as good as it's weakest link". It's probably safe to assume your ac power supply is poor-and since you haven't mentioned any I assume you have no power conditioning or isolation of digital. Without clean(er)ac power it's hard to evaluate the potential of your system. My suggestion is first buy conditioning. Next move would be the power cords to preamp and digital, hopefully with isolation value.. Then ic from digital to pre. Then ic from pre to amp. Only experimenting and listening will tell you the best bang for the investment.
