Several things could be tried:
--A great DAC
--Dakiom feedback stabilizers (30 day return policy)
--Tubes somewhere along the signal chain (However, my personal experience with tube equipment is extremely limited. For example, although I've heard of people using it, I don't know if the Musical Fidelity Tube Buffer works or not, and people had to tell me what "tube rolling" was, etc.)
In my system, the Dodson 217 Mark 2 D DAC makes a HUGE difference, but retailed around 5000 dollars when new. I got mine for under 2000 on a site called "Audiogon", and it's a wonderful unit.