Thinking I need a Sub...

There's about a $1900 difference between a pair of Boxers and Contenders. You will not get the bass extension or room pressurization from the Contenders that you'd get from the right powered sub(s) for less than that.

Since you're hearing your Boxer woofers distorting, you'd benefit from a sub that can send a high-pass signal to the Boxers and unburden those little woofers from attempting deep bass excursions.

One subwoofer product line that comes to mind is the new JL Audio E-series subs. They start at $1500 MSRP for the E110, which is only down 3dB at 23 Hz. According to the Stereophile test measurements, the Contender is down 3dB at 50 Hz.

The cool thing for your situation is that the E-series panel can accept low level input from your preamp, run it through a 4th order crossover, and send the high pass signal back to the amp that powers your Boxers. This will make a significant improvement in the Boxers' clarity and dynamic range.

I can't imagine getting anywhere near this performance from the Contender. You may need to take 2-4 hours integrating the sub/sats, but it will be worth it. Not only will the bass be stronger, more dynamic, and more extended than what the Contender can offer, you won't be adding cabinet noise to your mains, which is just as significant for low level detail. I've yet to hear a floorstanding version of a monitor (except Wilson, Magico, & co.) that is as clean and resonance-free as the smaller, simpler, and more rigid 2-way monitor little brother.

Ugh...now I'm really spinning.

Nola says the Contender extends down to 25hz. I'm not up on the technical jargon but that seems like it would be low enough?

Sorry for the noob questions.

^^^

That's great news about the SVS SB-2000. I wasn't sure if it high-passed to the main amp, but the user guide indicates that the line out high passes at 80 Hz. That would give the Boxers lots of breathing room. Everything below the botom string of a guitar would be handled by the sub.

01-14-14: Neo-luddite
Ugh...now I'm really spinning.

Nola says the Contender extends down to 25hz. I'm not up on the technical
jargon but that seems like it would be low enough?

I just checked the Nola website and it claims a frequency response of 35 Hz -28
Khz for the Boxers. No tolerances are given, so that 35 Hz could be 10-20 dB
down from the output at 1 KHz. The speakers could also have been positioned
for maximum room gain irrespective of imaging and clarity of the rest of the
audio spectrum. In speakers the two most often told lies are probably claimed
specs for sensitivity and bass extension. Read the Stereophile review I provided
the link for. The response curve is there to see. The bass is down -33 dB at 25
Hz, and -18dB at 35 Hz. It may be that with the right footers, a completely rigid,
masonry listening room (no suspended wood floors), and the speakers
positioned for maximum room gain, that you might be able to *hear* 35 Hz but
definitely not 25, and neither of these diminished levels at those frequencies
would begin to compare to the linear bass frequency extension offered by either
of the subwoofers Bob and I mentioned.

BTW, in response to your subject line, *everybody* needs a sub (preferably two).