Over the past 8 years, I've had a Toshiba, an Acer and a Dell. I found the Acer and Dell poor in terms of build quality. The Acer produced so much heat that it fried the Hard Drive. The Dell had a side-mounted audio plug, which gave in after 3 months as you invariably leaned on it when mousing. The keyboard of the Dell isn't very good either, with a few keys malfunctioning after 2 years.
So, on my experience, I'd opt for Toshiba, though my Toshiba was the first laptop I owned, so things may have changed. There's a couple of people on the forum that deal with laptops for work, and they may have a better idea of general brand reliability.
Regarding suppliers: I found
laptopsdirect pretty decent both in terms of price and service.