Upgrade for Thiel 1.6 - Or a waste of $$

A Soprano! Of course!

Great point - almost makes me miss grad school.

The best you can do is use your thiels with the subs for stereo (what is home theater anyway?)
Yes you need to drop the lowest freq. from your amps and speakers, the mids and highs will be unbelievable.
You dont have to change the design of the speakers; Imagine you have a sports car going uphill, without the lower frequencies your sports car will go only downhill, much faster and easier and you dont have to change the engine of the car!!!
Connect the Benchmark directly to a "y" connector, from there one RCA cable to the subwoofers and the other to a passive line level Cross over (or any line level XO) into the amps. Going down to 50 hz instead of 20hz will be a huge benefit for the amps, and the speakers will be happy also. I wouldnt try to go all the way up to 80 hz, it is more difficult to match the subwoofers the higher you go.
Remember the quality of the line level cross over is "very" important for a good sound!!!
Do this and you will laugh when you hear other much more expensive systems!!!! yours will be excellent!

http://www.t-linespeakers.org/tech/filters/passiveHLxo.html
This is what I am talking about...dirt cheap also!!

One of the most amazing (smallish) systems I ever heard was Thiel 1.5s with a single Vandersteen sub.

I had 3.5s at the time (I just repurchased a used set for my basement) and I liked the balance his set-up a lot.

A sub set up with the Vandy or something like it with the 1.6 should kick butt.

TD