latency is certainly relevant to this scenario since the sound has to go out of the computer to your amplification system… Digidesign hardware sadly do not come with ASIO drivers so you are almost certainly running under MME (you can confirm that in the Audio Device window).

I’m not sure what to suggest as there really isn’t any real solutions that does not involve purchasing a secondary audio card for ‘live’ use (without ProTools). You could try generic drivers such as ASIO4ALL in conjunction with your onboard card but I doubt the latency would be completely unnoticeable.