It's not that I don't like Cubase (my first sequencer was Pro 24 - Steinberg's first) but it is not really good at acting like a multitrack and depends entirely on the quality of the converters used. At least Protools HD defines this quality. My preference would be Radar but the Alesis HD is good too.

My instincts would tell me that you were perhaps not using enough of an analogue path for the results you want!