you need a very good quality DAC and monitors. you want the truest, most transperant representation of the music. you do not want to "hear" your equipment. you do not want the conversion or the monitors coloring the mix in anyway. This one starts at around $800
LUC-AD9624 and it just goes up from there.
I wouldn't suggest going below this as with converters you get what you pay for. that said, you can dip down under $100 with some m-audio and i think berihnger products.