Amp or HiFi reciver with line level sub out?

I’m trying to cobble together a home theater system using an existing sub-woofer with a built in amp. I want to get a pair of book shelf speakers and an amplifier that for said speakers but just send the low frequency’s at line level to the sub-woofer. Does anyone know of any amplifier or HiFi receiver that can do this? I don’t have a very large budget for this project so i would prefer solutions less than $150.

You might be able to find a Harman Kardon AVR lower end Denon on eBay for less than $150. They would work if you want a big audio/video receiver and you don't want a high wattage system.

http://www.ebay.com/itm/Harman-Kardon-AVR-146-5-1-Channel-40-Watt-PCO-235W-AV-Receiver-w-HDMI-Optical-/252210816261?hash=item3ab8efa505:g:fLoAAOSwAKxWbNUi