$50, pickup is free or you pay for shipping (in this region should be <$50), located in Washington, DC.
Fits perfectly in the passenger side of the trunk
Taken out of my '06 RX-8. Not sure if the trunk shape changed before or after, so that's up to you to determine.
Excellent condition.
No speaker included.
Has gold speaker terminals mounted outside with wires attached inside for your speaker.

I bought it from 4080 in this forum like 10+ years ago. It was the box described and pictured here (only difference between that one and mine is the grill)

 

Will ship this also-
Weighs 18lbs so shipping will probably be in the $30-50 range depending on how far you are from DC.