Did you disable the motherboard's on-board audio, in the BIOS, before you installed the X-Fi Titanium or the Creative Software?
Is it the Titanium-HD sound card or regular Titanium sound card?
Do you use this setup for just music or for gaming or for movies?
If you have the regular Titanium, then you might consider swapping it out for the newer Sound Blaster Z (better DAC chip).
I'm guessing the best way to improve audio quality is to replace the Solo 6c with better studio monitors.
Maybe try to find a good deal on some used JBL LSR305.