Subwoofer for classical music listener

(((For what it’s worth, I don’t like running my main speakers through some external crossover. I am concerned that additional electronics in the way of the main speakers will cause a loss of transparency. I let them play full range, and feed the subs by a second set of outputs on my line stage, directly to the amps on a pair of 15 inch sealed Rythmiks. I haven’t had the room measured yet, but I got them playing pretty good)))
Whart
 Sometimes we take 2 steps backwards to get 12 forward.
 Take a look at your in room response by downloading Vandertones
  write down 1 to 11 vertically on paper for left ch and 1 to 11 right.
Now Insert Vandertones Burned CD trk 1 to 11 try and get only 8 of 11 of these tracks over 70 db simply by adjusting the preamps volume control.
 once you have nailed 8 of 11 over 70 db c weighted slow your ready to write down the measurements for left and then track 16 to 27 for the right channel.
 
 Please feel free to share them here
 Best,
 JohnnyR

stfoth:  Thank you so much for your encouragement with the high pass option.  I had just about given up the hope of having the same quality with as without the subwoofer.  
Miracle of miracles! The high pass option seems to have done the trick.
Preliminary tests show no seeming degradation of the signal.
Of course, I just started testing and adjusting, but wow, the signs are very encouraging.
Thanks again.

And Al, of course thank you.  Wouldn't have happened without YOU!

If one's sub can be integrated using a mere 1st order high-pass filter (6dB/octave), there is a simple, easy, transparent way to accomplish that. Just solder a capacitor of the correct value (the formula for determining that value can be found on the 'net---it involves the power amp's input impedance and the desired corner frequency) on the power amps input jacks.