Hi

I used an ART Tube Mix as my interface plugged into a PC. No lag that I have noticed.

I have used and still use Audacity but only because I am familiar with it. I am starting to learn Cubase and am playing with Reaper as well. Audacity has been ok but as I progress I am finding its limitations.

I'm not familiar with GB but Carl says you can get milage out of it so I would take his word on it and try his suggestion before making a switch. The only reason I am starting to move away from Audacity is because of the limitations I am noticing.

Good luck