Don't know about the NP booms quality, but I can say that nowaday almost all brands sells booms with 60 cm extension.
I don't like so much the NP maketing style, as I still have a NP 57 cm carbon base extension full of written warnings about the dangers of using it with other brand products... Used for may years with a cheap NS mast and no problem at all. Second, the older boom calmps of NP looked very poor with their plastic and economic system (don't know now).
Here in Italy, but also in all Europe has a well reputation the italian Tecnolimits, that is a brand born many years ago right producing ONLY their own booms (it's a specialized factory of alloy products also outside our sport - now they also sell masts). Here the King Revolution Ergal model is known as one of the best booms available, and the fact that also Hotsails.de sells it in Germany and outside can be a witness of his quality.