Accessories4less.com has some
factory refurbished, factory warrantied Onkyo and Denon HT receivers in your budget range. Those should have subwoofer line outs. They have a good reputation as a vendor (my family has used them twice to buy receivers, too).
I think most 2 channel stereo receivers in your budget range do not have subwoofer out. But that's typically not a problem because you can easily find a subwoofer with speaker level inputs. Then you hook your main speakers to the A left/right speaker output on the receiver, and your subwoofer to the B left/right speaker output on the receiver. Other than Craigslist, your best bet for a 2 channel receiver is accessories4less again. Look for Onkyo.