Using Windows Explorer to burn my CDs...should I be using a more 'sophisticated' burner?

The 1st question asked in the burn is "is this an audio or data CD?"

As far as the quality of the gig mp3s - they just aren't 'clean' sounding... I guess muddy would describe them... I plug the SONY DVD into a regular channel of the Mackie mixer, so I can adust the hi/low for each song if needed...but that only results in too much treble/bass... Do I need some sort of 'interface' going from the audio out of the SONY into my mixer? The vocals and piano sound really clean/clear coming out of the JBLs, with the BBE doing its thing... so it is not the PA....

I use MP3Gain to level out the volumes on my gig CD - could that program be 'affecting' the final product?
Even with that, I find I'm always scrambling to adjust the volume knob on the mixer once the song clicks off... I don't understand this volume discrepancy from song to song... is there a 'volume' setting that controls how loud the song gets rendered to a WAV? When I load in the songs into Audacity (to make MP3s) the wave form varies widely from song to song?? And when I bring them into MP3Gain - the listed volume dbs also differ greatly - some at 90.x, and others at 79.x - so SOMETHING is affecting the rendered volume...

Hope that answers some of the questions... appreciate any/all feedback here...