Wow... I am sure there are people who are not going to like what I have to say, but there are many posts that seem quite out of line from my perspective. My husband is a licensed contractor - a very small one at that. He specializes in interior work, and willingly bends over backwards to accomodate and be flexible for people. He meets with whoever chooses to be present, and would be skinned alive by me if he was ever sexist in any way. That being said, there are a few things I noted of importance in this series of posts....
1. The OP seems to be choosing to contact high-pressure "sales" type of places. I would HIGHLY recommend, as one other poster has, that you look for a "licensed contractor" rather than a sales office to do your work. Some sales offices contract others to do their work, while other offices have their own employees do the work. Those that have their own employees...you really cannot guarantee what kind of work they do, as they are likely making minimum wage and/or cash when they show up (honestly, trust me). And just because they say they have a warranty, well that doesn't mean it is going to be an easy task to get things fixed. If they contract out the work, you are essentially paying a "middle man" - the sales office. There are many ways to find licensed contractors (key is the license) in every area, and could be as simple as going to Lowes/Home Depot and asking for names of people who do that type of work. I still HIGHLY recommend you get at least 3 bids, and trust your gut feeling when talking with people. The licensed contractor doesn't work for a specific brand, and therefore could give you several bids with different brands of products if you so choose - and will be able to discuss the pros/cons of each.
2. And just remember that people in the construction trade are just that - people. They have families, they have financial concerns, they have needs and they are PEOPLE. The rudes contractors...well you I would agree with you. But just try to put yourself in their shoes - and try to understand why they would not want to make several trips to your house without getting paid a dime. They may get the job, but they also may not - for reasons other than the kind of work they do. There is a lot of time and money invested in putting together bids, and oftentimes I think people don't fully appreciate that piece of it. Again, this is just from my perspective as the wife of a contractor.
Anyway, that is just my two cents worth. To the OP - you obviously know exactly what you are doing, and appear to be able to understand many of the technical things discuss. Way to go! I am on the other side of that...my dear old hubby is the expert, therefore I choose not to pay much attention!