You should be careful about asking for estimates. Some of the companies that do this are very aggressive. You will often not be dealing with a situation of “here is our price, call us when your ready” but rather a situation of “you can only get this price if you sign right now!” and a salesman who won’t leave your house unless you sign or call the police. Read online reviews of the company before you ask for an estimate.
You should be wary of any place that demands that both husband and wife be at the presentation.
Find out the preferred local suppliers of established small builders and renovators. The window companies that those guys use are the ones you want. Big builders have a lot of clout and you may not necessarily get a good deal / product out of the suppliers they deal with. The Window companies serving small reputable builders and renovators are going to have quality product and service suited to smaller projects.
Also understand that when you have chosen a supplier / installer they are going to have to remove all the interior trim around the windows being replaced in order to get an accurate measurement of the rough openings. Going by outside window frame size is not sufficient.
I want to know, how much for the doggies in those windows?