There was a cabling problem in my setup causing the low output. The 970 went single-ended into the red input on the Dayton and I took the white output of the Dayton to the second sub. Actually I was suprised it worked at all.

Reading the Dayton manual I found that they recommend a Y-cable from the source to BOTH inputs on the amp. I tried it both ways. The Y-cable hookup resulted in more volume from the single subwoofer. Strange: I figured that 1 + 0 = 1/2 + 1/2 but obviously there's something in the Dayton amp that wants both inputs.

So now I added the second sub (the Infinity) in a daisy chain configuration and ran single ended and "stereo" configurations from the Dayton to the Infinity. The Infinity was louder when I ran both connects ("stereo" connect NOT Y-cable, NOT single ended).

According to the docs if you hook it up this way the low level outputs are unmodified copies of the input signal. i.e. no gain or filtering is applied.

Hope that helps. Good Luck

p.s. I was quite suprised by this and now I want to add the second sub to my setup