Why Kinergetics SW-200 clipping?

I'm a newbie and have a simple question about clipping.

I have a Kinergetics SW-200 sub (four 10" speakers, 200W kinergetics amp). They seem to clip really easily. These have always been rated as a high-end sub, but they don't do it for me. I want to "feel" the bass in my home theatre setup.

I'm in a fairly small room (15 x 15) which I know limits the level of bass producability. Does the small room also mean that the subs clip easier? Or am I pushing them too hard trying to get bass out of them that I can't get in such a small room?!

Any insight would be great.

Thanks.

John