I am planning to replace 2 toilets with Toto Drakes. I went to a nearby plumbing supply house and was quoted a price of $349 for the ADA model, which I want. I then talked to a plumber to get an installation quote. He said he could supply 2 "Contractor Grade" Drake toilets for $300/ea. What does "contractor grade" mean, and is there a difference between that toilet and the one I can purchase myself? Thanks for any help.