Stereo line level and preamp output question

I have a Sony head unit with two line level outs and two preamp outs. I recently added a amplified Bazooka Tube. I have both Line level outs hooked to the front and rear speakers. There is no sub-woofer preamp out so I hooked the bazooka tube to the rear preamp out. Both line level outs are still being used by the front and rear speakers. My question is can I do this without causing any problems? My stereo seems to cut out at high volumes and I don't know if this is caused by the the current installation method or if I need a capacitor for the bass hits. I am thinking about installing a amplifier for the front and rear speakers and don't have enough preamp outs. I think I need to install a crossover with high, mid, and low pass.This way I can split the rear preamp to go to the amp and the bazooka tube. This would also allow me to segregate the frequencies to the various speakers. Does this sound right and what is causing the cut-out? Is it the way I have it hooked up or do I need a capacitor? Help, answers, and dumb comments would be greatly appreciated.

you're probably overheating the internal amp, how high do you have the volume when this happens?

a cap is most certainly NOT the problem, people seem to think they're some magical device that will solve any and all problems....they have a very very limited range of uses, and even then it's pretty questionable whether the cap does anything or not.

Volume level is probably around 75%. Would it overload the internal amp even though I just added the Bazooka tube to the preamp. Isn't the preamp just what it says? Prior to the amplifier. How would that overload the amp? Just curious to your thoughts. I agree with you about the cap. It was just a thought. I understand there purpose but I don't think the Bazooka tube has enough draw to overload the electrical system. Plus none of the interior or exterior lights dim when the stereo cuts out. The stereo doesnt seem to cut out completely either. I guess I should hook up a meter to see how much current is being drawn. Will installing a crossover eliminate the problem?

The bazooka isn't the problem, like you thought it just takes a very very low power signal from the headunit, a few milliwatts (one one-thousandth of a watt) at the most.

If the volume is at 75% overheating could be the problem, if you leave it around 50% all the time does it still cut out?

It will not cut out at any level below 75%. It does not cut out at 50% at all. It seems to happen at over 75% output and takes maybe a half hour at that level before it cuts out.

definitely overheating

the only way to keep that from happening is to not turn the volume up so high or to get an external amp for your speakers