...I'll beat acudeftechguy to the punch on this one and recommend the Def Tech super towers. The built in subs are simply wonderful, and they have the option to run a lot of power to them...
This is what happens when I'm off work for one day.
I think in terms of midrange/upper bass and high frequency, almost all speakers within the same price range will have more in common than not. I think the biggest difference is in the lower bass frequency.
When I look at the ultra high-end speakers, the one thing a lot of them have in common is the built-in powered subwoofer. This is how they can produce bass down to 20 Hz or below.
Now if I were rich, I would get the Bang & Olufsen BeoLab 5 (18 Hz - 20 kHz +/- 3dB, $8,000 ea). This baby not only has a built-in 1,000 watts powered subwoofer, but it also has a built-in 1,000 watts powered upper bass, a built-in 250-watts powered midrange, and a built-in 250-watts powered tweeter.
Oh yeah, I love my BP7000SCs & their 1,800-watts RMS built-in 14-inch subwoofers. People have to actually listen to these babies to believe the kind of bass they can produce.
I can get the BP7001SCs (22 Hz - 20 kHz +/- 3dB) for $1,200 each at my local HT store. They are similar to the BP7000SCs, except they have the 1,500-watts 10-inch subwoofers.
The Aperion Intimus 533-PT speakers (30 Hz +/-3dB, $600 ea.) also have a built-in powered subwoofer.
But what is interesting to me is the Def Tech BP10B. These babies don't have a built-in powered subwoofer. And yet Julain Hirsch & the Stereo Review Lab measured their frequency response as 25 Hz @- 3dB, & 20 Hz @-5dB. How on earth can they produce bass down to 20 Hz @-5dB without a powered subwoofer? And the price? I can get these for $400 each at my local HT store. Are you kidding? Imagine having a pair of these for $800 plus a SuperCube I subwoofer (20 Hz @-3dB/$800 at my local HT store) for $1,600?
For pure 2-ch music, a pair of BP10B would be fantastic (20 Hz - 20 kHz +/- 5dB). For movies, the additional SC-I sub would be awesome.