FYI "quad-butted" isn't necessarily higher-end than double- or triple-butted tubing. If I remember correctly it just means the tubes are slightly thicker where the water bottle bosses are. Doesn't necessarily lend more strength than a regular double-butted tube with a reinforcement braze-on at the bottle boss, and is probably slightly heavier.

After looking around for a bit it could also mean just different thicknesses for each butt. Sort of how Ritchey markets it's custom butted tubing