Hi. Just a basic question. I have a presonus firebox and a firestudio. I am going to buy some high quality a/d d/a converters (Not sure which ones. Thinking of getting a Universal Audio 2192 for now, but am also looking at the apogee da x16 and ad x16 and an RME 8 QS M) and some preamps (api 3124, neve 2-610). Do I need an audio interface, or do the converters work in their stead? What do the pros do?