As everybody else has said, the audiobox is a 2x2 interface... you want something with four outputs in order to monitor. Best choice for on the cheap is a audio 2, after that, look into the audio 4, audio kontrol 1 (if you need a mic input) or maybe a fast track pro (don't have any experience with this card, but others have said it's ok). I'd recommend a firebox, but if you don't have a firewire port that's kinda out of the question.