Believe me, I've been here before...asking the exact same questions. It's not cheaper to build your own...just check around on Newegg.com and see what you can find. Even if you find something with min. ram, it's cheaper to upgrade yourself. I find that Asus tends to have the best build quality and price/performance ration, but that's just in my experience...there are many good brands...but I find Dell to be the worst, again, in my experience with them. You can buy a great laptop for a grand...
EDIT: As for monitor size, as others have said, 17" is overkill unless you are using it as a desktop replacement....17s usually eat batteries quite fast...15.4" is the way to go.