Limewire player fidelity

I am in the process of converting my music collection into all digital. I am converting all my CD's and MPEG files to the Apple lossless format and using the itunes player. I am trying to get the best fidelity I can while connecting my laptop to my stereo. I have been perplexed by the drop off in fidelity when playing songs via Itunes or Windows Media Player as compared to a cd player hooked directly to my stereo. I even purchased a Stereo link digital to analog converter hoping to improve the sound quality and it did not equal the same fidelity as the cd player.
Then I just launched music through the Limewire player and lo the music came across louder, brighter, crisper and with more fidelity. Does anyone have an explanation for this? If so how can I get this clarity consistently without necessarily using the Limewire Media player.