Here's what I think the best way to handle the situation is:
1. Acclimate the livestock to your tank when you get them. Do daily water changes to keep the ammonia as close to zero as you can. You may even need to do water changes twice a day. So, make up plenty of saltwater (it needs to mix for at least 4 hours outside the tank with a powerhead before you add it). A little Amquel may help keep things in check, but don't rely on it solely.
2. When the live rock arrives, cure it in a bucket (or large rubbermaid) with saltwater and powerheads. Do not add it to the tank until ammonia and nitrites are at zero. Live rock, once it has been out of water, becomes uncured. It needs to be recured before adding it to a tank with inhabitants. Even though you bought it as cured, it won't be safe to add to your tank for a week or so.