I did the windows in my house.
I ordered Pellas from Lowes. I don't think it'll matter much where you order them from, although you'll probably get better insight and guidance etc from a Kelly Fradet or other supply house, but you'll pay a premium there, too. I had to make a couple return trips prior to ordering because I didn't know exactly what to look for and the guys at Lowes were no help at all.
I wouldn't get Pellas, though, unless you're just trying to flip the house or something. They are fine, look nice etc, but I've found a couple quirks that I notice and I can be a perfectionist. Some of them aren't perfectly square, some of the plastic welded seams are a little rough, and some of the screens are practically diagonal. All little complaints but you get what you pay for. IF this was going to be my "forever house" I'd be annoyed but they're all little things that don't really matter other than aesthetics. They perform more than well enough for what I paid.
We got all 19 of our windows and the big picture window for right around $3k. They are middle of the road model and they have some extra features; annealed (tinted), triple glass on the picture window, shatter proof on the first floor and over the deck, gas filled, double hung, etc) That includes the hardware, the lower floor sills I had to replace, and insulation too. We had a 10% off Lowes coupon from moving and they had a 25% off customer ordered windows deal at the time, so we made out like bandits.
American Window quoted me $6k (including labor) without the picture window.
Im slammed up until July, but I can come take a look if you want after that when I get some time. I can help you measure and get you ready to order, and when they come in if I have time I'll do a couple with you to get you rolling.