The Achilles Heel of the KEF's is the T33 tweeter, which should have been put to sleep a long time ago. It's a good, but not great tweeter. I've had probably a dozen of them, for the simple reason that they are ubiquitous throughout the KEF line and I've owned a lot of KEF speakers. At one point I think I had 8 of them lying around. Everything else about the 107 is exceptional.
That being said, I would still take the KEF's over the Yamahas. I find the sound of the 1000's unforgiving, to put it mildly. Too analytical. The KEF's blow them away in terms of bass response and sound stage. The Yamaha's on the other hand have a superb mid range. You'll not find either speaker a bargain, unless you get real lucky. If you want a really interesting and exciting speaker, check out the Yamaha NS 80X. Carbon fiber composite 12 in. woofers, ported design. My buddy has the only pair I've ever seen. I think they sound wonderful. Another great alternative to the Yamahas is the Mitsubishi Diatone line. The particular model I've heard is on par with the NS-1000. 12 in. acoustic suspension woofers, 4-way with metal dome mid, tweeter and super tweeter.