Tweeter height...align with ears?

There is no standard rule that can apply towards all speakers and listening rooms. As you move off the direct line from the center of a tweeter the high frequency response gradually falls off. This applies to a vertical offset which is affected by the speaker's height as well as horizontal offset by setting the desired toe in angle. So you can fine tune the speaker's high frequency balance by experimenting with height and toe in. Depending upon the speaker's design and crossover type there will also be an optimal height where the drivers blend is more seamless, meaning that you can't easily locate the sound coming from the individual drivers as the sound field becomes more coherent. So you either need to follow the specific speaker manufacturer's recommendations or experiment to find the best position in a given room.

Bill is correct. Rogers recommended the woofers in my Studio 1s be at ear level. I've found that to be pretty good but had to do a lot of adjustment with toe-in and surface distance to get them where they perform best. It's all part of being an audiophile.

Good luck & happy listening!