Would you really consider Engl, VHT and Framus "Boutique" as such? Boutique amps to me would mean more of a smaller company, hand building amps. Engl aren't hand wired either, and they're actually one of the cheaper brands here in Europe. They'd only cost a lot more for you in the states, while here, a Mesa Boogie would be far, far more expensive than an Engl.
A Mesa Road King is nearly TWICE the price of an Engl Invader to us Euro folks.
I think a company comparable to the above brands would be Soldano, who've been at it for years, and nobody looks back on them as a fad.