The Innuos reclocker should be able to improve the sound of a audio streaming from a computer It is very pricy so it may not be the perfect choice for your budget but it may be worth thinking about. There are other brands that are cheaper that may or may not sound as good. I have not tried this but is using an Audioquest Jitterbug which improves the sound for me.
http://hifiknights.com/reviews/accessories/innuos-phoenixusb/
There have been threads about this before.