IMO headphones make it much easier to do critical listening, just because critical listening through speakers can be complicated by bad placement, background noise, and all sorts of environmental factors that are better managed through headphones. You can also get some very good headphones for the same price as some very crappy speakers. I really like my Sony MDR V6's for audio work. Not the best thing out there by a long shot, but still awfully good, pretty cheap, and nearly indestructible. YMMV, of course.