By underpowering the speakers, you may not get the volume you want with limited power. The user then wants more volume, turns the volume up and the amp tries to produce more clean power than it is capable of so it clips and causes distortion. Now, this in turn gives the user what they desire because distortion is actually louder. However, it is not good for your amplifier and for some people the sound is unacceptable (hence why my amps are capable of 2-3 times the RMS rating of my speakers). But yes, if you never exceed the amplifier's clipping point (which is hard to judge by ear) then it should be fine...you just might not get the output or performance you desire. Plus if your amp is running full tilt a lot of the time (clipped or not) it WILL run hot and likely shorten its life...

As for your situation, keep in mind that the enclosure plays a huge roll in power handling. If you use a large sealed box, then the woofers will run out of excursion with low power. Use a small box and you need a ton more power to get output. Example: A while back I used 2 JL w1 subs rated for 150w RMS each (300 for both) in 1 cu ft sealed each. I had them in half of that airspace and they were taking up to 800w RMS fine. On a side note, I dont think those sonys could actually handle 1200w RMS or even close to it...

 

I guess the point I was getting at was (for example) a 400Wrms @ 4ohm amp works no harder to push a 1000wrms subwoofer than a 1200Wrms @ 4ohm amplifier under proper tuning because a woofer does not "draw" power from an amplifier. It simply utilizes the power given, kinda like with a 6V light bulb connected to a 1.5V battery. Therefore the only way an amp will work harder is if the user cranks the gain and bass boost and clips the signal, in which any amp will go nuts unless the woofer burns the voice coil first. I guess that's why so many people hate Sony equipment, because they see 760 watts on the box, not knowing it pushes only 125Wrms a channel x 2 @ 4ohms, and get upset when they hear the clipping which is fairly easy to hear with low power. But yeah that's kinda what I was getting a second opinion on.

For the subs I had, the Boston Acoustics C110 is a 10" woofer with a PR on the back. I had two of them, SVC 2ohm each. The 550S went bad over time I guess. That's all I had hooked up and I was told not to mess with the amp (those were my newb days) or try to run a bass boost ****. After those went, I had a 1.75cuft ported box built for my Power HX2 at Ultimate Electronics. That lasted 30 minutes before the voice coil burned. When I got home, I put my Punch HX2 in the box and it lasted 10 seconds. So I built a box for my four 10" Thunder 8000s, sealed, 4 chamber, 0.65cuft, and that barely lasted as well, only 1 sub survived. So I called up the guy who sold me the amp from Ultimate Electronics and he told me that my amp is still under the in-store warranty. Without anything, I decided to install my Power 1001bd amp I bought as a reefer on ebay and that's when I learned about clipping. I got two 10" Sony XS-L1055G and two 10" Sony XS-L100P5 subs (I had to look up the model numbers for those) wired in my 4-chamber enclosure stuffed with polyfill, the 1055's @ 0.5cuft and the P5's @ around 0.6cuft to tighten the response. The clipping sounded ugly, and I was told to set my headunit how I wanted it in terms of eq, and turn it up just higher than I would ever listen to it, then turn the amp gain up with 0 boost until it distorted, then turn the gain down a pinch and I'm set. That system is long gone since I'm more of a family kinda guy and I've toned it down a bit. But that's the story behind that. Some amps just have lemons in them I guess.