I have the Kef Q150 (msrp 600) and also the Triangle Borea BR02 (msrp 449). I prefer the Triangle, even though they cost less. The Kefs are good as well, but are not as good in the treble as the Triangles are, to me anyway. I am using a Marantz integrated amp, which is a bit on the warmer side, so perhaps that is why the Triangles sound better. Bass wise, I would say both are comparable. I use a sub. They are 12 inch bookshelf speakers after all.
Not sure about the Yamaha amp as far as its sonic signature. If it is on the brighter side maybe the Kefs would be nice with it. If it is neutral or warm, I'd go Triangle. Audio Art Cables sells the Triangles, often at a discount of 10%, sometimes 15%, so they come in at $400 or less. That said, the Q150 can often be found at half price as well.
Not sure about the Yamaha amp as far as its sonic signature. If it is on the brighter side maybe the Kefs would be nice with it. If it is neutral or warm, I'd go Triangle. Audio Art Cables sells the Triangles, often at a discount of 10%, sometimes 15%, so they come in at $400 or less. That said, the Q150 can often be found at half price as well.