Digital idiot wants to KNOW: upsampling?

In my quest for "perfect sound forever" I see that the big rage is upsampling. So how does this work. (The Sine wave graphs in the mags look so pretty) I see D/A converters that accept 96/ ??? Does this mean some CD players put out this? and what if you have an output of 96/??? and you D/A is an old outdated one... does the 96 get downconverted to ??48 (So it seems in my Acdom GDA700?).
I want to gain some sort of understanding how these multiple rates mesh together. Or just point me to a site that helps? Also it seems some D/A's do the upsampling and some just 'accept' upsampled data. I am comfused. Help me (so I can spend another $3000 on a MSB Platinum and not get burned.)