Hardware monitoring is definitely a good thing, especially if you are recording from external sources to existing material.  If you have a vocal or an instrument being recorded, you want the hardware to send the monitor signal back out rather than route into the software and then back out, that introduces latency and additional resources on the CPU. A good sound interface with zero-latency monitoring usually provides some sort of mixing interface for the hardware so you can create a monitor mix of the pre-recorded material coming from the DAW and the incoming live audio.