Okay. so you are using a laptop, ripping mp3's from CD's, and downloading mp3's from the internet, and then listening to the songs directly from the laptop in mp3 format, correct?
You do realize that laptops vary significantly in sound quality, right?
Here's my "pipe dream" suggestion... this is a long term solution, probably well above your current budget, but you can do parts of this without spending lots of money.
begin ripping your CD's (using the original CD's) with Exact Audio Copy, and using FLAC to encode them, and Foobar to play them. Then, buy a Headroom Bithead or Total Bithead, or one of the other USB DAC/Amp combos suggested here. Then, if you need isolation or have other people near you when you are listening, get a set of closed headphones. Otherwise, get a set of open headphones. Listen to them through the Bithead with the headphones.