Go with the top three Advanced Armament, Yankee Hill, or Ops Inc. Find out who has the 5.56 set up you want and purchase it IF IT is stocked at that dealer. If you purchase from a dealer that has no stock you could wait for weeks, months, or yes a year. I have the AAC Omni but it is NOT the cheapest. It on the other hand is a great suppressor. Decide if you will ever put it on another firearm. When purchasing a Quick Disconnect (QD), you will need to buy additional mounting (flashhiders) for each gun. Omni is a QD without any additional hardware. Mounts on the original A2 birdcage. You can also get a threaded suppressor which will can save you a few dollars. The attachments usally will add $60 to $80 to the suppressor. Look up the manufacturers of suppressors and review their products BEFORE making any decision. This will save you time and money in the long run.
Enjoy your shooting