amplifier clipping or sub bottoming out?

I have an old fosgate punch 100x2 amp pushing an infinity kappa perfect 10.1d (dual4ohm) in a .6cu. ft. box ( infinity recommended inclosure specs)and it dosen't hit very hard before it sounds like its bottoming out. It has great s.q.though. I asked infinity and they said that my amp is probably clipping and causiing the distortion. The amp is 200watts rms at 4 ohms bridged, or 100 rmsx2 @ 2ohm stereo.And from everything I've ever read or heard, the old fosgate amps are way underrated, so it should be close to matching the 375 rms of the sub...I have the punch 100 pushing 2 audiobahn 400w rms 12's in a sealed box @ 2ohms stereo and it POUNDS, very low, almost inaudible, and dosen't distort, so if anyone has any suggestions, please let me know.Thanks

are you sure the box is sealed? what is the freq set at? crossover set at? what size power? how long of ground and how good connection?

Box is sealed very well, input cup leaks just barely, there is no filling in the box. the crossover is set at 90hz, power and ground are fosgate punch 8ga with good connections, not cheap fosgate either ground is only about 1 foot long, maybe 14 inches.  Are the old fosgates (black ones, look like george forman grills) as underrated as many people say, I think the ratings are based on 12.6volts, thanks

 I have always been told that the older fosgate amps, early-mid nineties, are very liberal on their power ratings, and have great sound quality...I have also heard a punch 100 out pound a pioneer 760watt max, and a crunch 1200watt max amp, making much cleaner deeper bass from a smaller amp pulling less current. Why is that, are the newer fosgate amps just as good? And has anyone ever bench tested one to see actual rms and peak ratings? I  also have read about people running 2 ohms bridged without a problem, but fosgate says that it is only good for 4 ohm briged. If anyone has input or opinions, please chime in

Hey...I don't mean to beat a dead horse, I know that the old school vs. new school thing has been discussed over and over, but no one ever has any real, solid evidence for either side, like **********bench tests********, I have a punch 100x2 and a punch 200dsm and am curious if they are everything they are built up to be.

older fosgate amps are better & sound much cleaner in my opinion. i used to own the punch 200 dsm & punch 150. very nice amps.

Going back to your original question, personally I like to build them (boxs) a little bit larger than what the manufacturer recommends. Seems to me like every company tries to make subs that will fit in the smallest box. I used to go by the recommended sizes but I have had the same thing happen that you are describing when I don't up the air space some. I would try making another one and see how that sounds.'85 Toy