I recently fell into this trap again myself, I'd ended up with a spare set of disc brakes and disc equipped wheels, a quick look around the shed and I thought 'yeah, there's a whole bike here minus the frame'. So I purchase a new frame, turns out i also needed a rear mech, cranks, handlebars, headset, saddle, the list continues. After all that the bike has turned out nicer than i thought so some components dont do it justice...