Troy - Let's start with the Physics of a loud speaker, and what we are asking of it. We often see our hearing as being from 20-20,000 Hz. In reality, most of us hear little above anywhere from 10,000 to 15,000 Hz. Of course, this has been blind tested. My last test showed about a 14,000 Hz "ceiling".

In terms of real speaker performance, we have 10 octaves that have the following spans from 1 to 10:

1: 16-32 Hz
2: 32-64 Hz
3. 64-128 Hz
4. 128-256 Hz
5. 256-512 Hz
6. 512-1024 Hz
7. 1024-2048 Hz
8. 2048-4096 Hz
9. 4096-8192 Hz
10. 8192-16384 Hz

Anything above or below those frequencies are typically irrelevant, but if a speaker can reproduce them cleanly, it would be considered a plus.

Next, let's look at the size of the wavelength at the deepest frequencies:

16 Hz: 70.625 feet
20 Hz: 56.5 feet
40 Hz: 28.25 feet
64: Hz: 16.75 feet

I stopped at 64 Hz because 16-64 Hz represents the two lowest octaves of our hearing range.

Now let's look at the amount of excursion based on frequency: Every time you halve the frequency, you need 4 times the excursion to achieve the same SPL.

For example, look at the 64 Hz bass tone - which is a 17.65 foot long wave length. If a driver requires 0.25 inch to achieve, say, 105 dB at 64 Hz, the same driver will require 4 inches for 105 dB at 16 Hz.

In my personal system, I am running a pair of LFR-1100's with an amp that can deliver 125 watts into EACH of the 6.5 inch HP woofers (it's a 375 wpc amp).

I still operate an EP-800 crossed at 40 Hz to the LFR-1100's, and the effect is not subtle. Not only does the bass hit much harder and deeper (it is essentially a 1.33 octave range), the subwoofer is taking the load off the main speakers, which allows them to be even more dynamic.

You have a tremendous system. Would you give up the 1.33 octaves that span from appx. 6600 Hz to 16,384 Hz? Looking at your system in a linear fashion during more demanding scenes, you currently have about a 40 Hz floor, giving up the 1.33 octaves below 40 Hz.

A single EP500, EP600 or EP800, properly dialed in, would make a huge improvement in your system. I would recommend a 60 Hz crossover, and let the subwoofer handle the 16-60 Hz material.