Subwoofer out gain?

[godslayer]

Hi friends,

I have Kenwood's RSe7 amplifier which seems decent for my listening habits(it has a pure A mode which puts in 7+7w at 8 ohm on each speakers.. i am using hi efficiency philips drivers and they do sound pretty well.

Anyhow, due to low wattage, the bass reproduction is very bad and low frequencies arent produced very well so i am thinking of making and designing a dual tda2050 Sub for the same,there is a pinout(RCA) towards the end of the amplifier which reads SUBWOOFER PREAMP OUT. a compatible subwoofer is kenwood SW500 (unfortunately unavailable in my country as this itself is an import) so my question is, if i supposed make a dual TDA2050 chip amp, can it be driven directly by the gain that is received from the output of the amp at the subwoofer out rca jack omitting the preamp circuit? because i am trying to minimize the components (especially preamp which requires a separate power supply and adds complexity to the circuit)