a cheap fix would be to use a z-man ase tubed buffer-stage. this was the only way i could listen to cd's on my system, prior to getting a tubed preamp. (musical fidelity also made a similar product). these show up on the used market for ~$100. i'm not even sure if it's worth it for me to bother selling mine - i will prolly use it in a future secondary system.
another nice thing about the preamp, besides making my cd's enjoyable (thru a very modest nad cd-changer), is that my vinyl & my tuner have also never sounded better! if ya *do* listen to other sources, spending lotsa money on a cd/dac upgrade won't help *them*
doug