low freq problem

I have 2 12" cvr kickers, 800watts each, hooked up to a 1600watt boss amp and 4 some reason when i play certain song with low bass the woofers dont sound good.......they almost sound like their "bottoming out", but i dont wanna jump to conclusions. Anyone have any advice or knows whats going on.

My guess is that you are hearing a clipped signal.  It's surprising how mechanical clipping can sound.  Make sure the gain is set correctly and that the bass boost is turned off.  The next possibility would be an improper enclosure as David mentioned. 

They are both in a sealed enclosure. But my guess was that the box may be the problem 2, it may be too small.

Too small an enclosure wouldn't cause the subs to bottom out.  In fact the opposite would be true.  Efficiency would be lower, as would low frequency extention where you get woofer excursion from.  Where are you getting your signal from?  Are you using an aftermarket head unit with RCA outs, or are you using a hi/low converter?  If aftermarket, what is the rated voltage on the pre-outs?  Where is the gain set on the amp?  Do you have the bass boost on the amp turned up at all?  Who did the installation?