I'm using a JBL BP1200 to power 2 12W6's in my wife's car. It's a little overkill for W6's, but since its her car and she rarely cranks it up, it's all good...

A JBL BP600 should work very well with any 2 W6's because of the voice coil configuration. Wire eack sub to 3 ohms and parallel them both down to 1.5 ohms. 300 watts a piece should be fine...