I had a spell with a 200w combo, for boot of car reasons, which I thought would be fine - and to be fair, often it was. But sometimes it just wasn't! I do try to turn right down for the greater good of FOH (its not easy is it?!) but I think there are definately times when some extra backline really helps - instances of crappy monitors, or sound techs tweaking the settings so you can't hear a thing and then wandering off for a piss, weird room accoustics (the deaded high-roof L-shape venues), desk problems, house PA on the blink so you have to rely on a hastely acquired back-up, whatever. On balance I think there's much to be said for having access to a bit more oompf, even if its rarely called on. Peace of mind. And, as others have said, you can get a better sound cos of headroom thing too (even if no one else notices!). Obviously you don't want to look like a overcompensating tw*t in small venues, and depends on the band, but stage furnature is appropriate is some settings too, cos its part of the show. I've had the best results and flexabiliy with a mix and match / modular set up.