When I say 'speakers have similar voicing', I mean they sound similar across the mid-range – the most important part of music. In 2-way speakers, the crossover is right there, usually in the 2 to 3 kHz range. This audio range, in the middle of the speech-discrimination range, is where human hearing is most sensitive. In good 3-way speakers, the mid-range driver handles most of the speech discrimination range. It raises the mid-to-tweeter crossover to a much higher and less noticeable frequency, and allows selection of a bass driver that can go deeper without distortion or break-up noise.
All of Dennis's Philharmonic Audio and Salk speakers share well-designed crossovers, without audible dips or peaks across the crossover range. They perform well on-axis (directly in front of a speaker) as well as off-axis (off to the sides by at least ±30°). Good off-axis performance is critically important to a speaker's ability to create a wide and realistic sounding audio image, or in stereo a 'sound stage'. Speakers lacking good off-axis sound can make music sound like it's coming from tiny musicians inside the speaker cabinets. While speakers with good off-axis sound make those musicians seem to emerge from the cabinets and join you in your listening room. These features makes Dennis Murphy's designs stand above many other – but not all – commercially available speakers.
Edit: If it isn't obvious, I very much like speakers that are good at creating realistic images and sound stage. For what it's worth, the Philharmonic Audio BMR Monitor and BMR Tower speakers are the best at this among any of the speakers I've heard.
More money gets you better performance at the bass and treble extremes of audio. The drivers are more expensive, and deeper bass also adds to cost because it requires larger, heavier, and sturdier cabinets. Many floor-standing speakers can deliver bass down in the 40-50 Hz range (if the manufacturer is honest about performance). More money gets you down to the 30-35 Hz range. And much more money gets you down to about 25 Hz. Below 25 Hz requires crazy money. That's what subwoofers are for.
More money also gets you lower distortion and a more detailed sound, leading to a more transparent sound. For example, in the original SongTower, the very good quality
Seas ER15RLY mid-woofers cost about $79 each (retail). The Veracity ST speaker uses the excellent quality
Seas W16NX mid-woofers that cost $285 each. The ER15 driver has a smooth sounding paper cone with added reed fibers, and the W16 driver is made with a magnesium-aluminum alloy cone that goes deeper, has lower distortion, and has an overall more detailed sound.
Each speaker model has a custom designed crossover that blends the performance of the speaker's drivers. Different combinations of drivers require different crossovers. No standard off-the-self crossovers are used. That's an essential part of any good sounding speaker.