Yes and no. Maybe. What you describe is generally referred to as 'bridging' which can greatly increase the power output to the sub. But it depends on certain factors. The amp needs to be bridgable, if its not, nothing good will come of it. The amp and sub must be compatible, with a 4ohm sub, bridging means the amp sees 2ohms on each port, so the amp must be rated at 2ohm stable, or nothing good comes from that either. If you meet the above conditions, the only remaining one is hookup. You'll either need the manual, or if lucky, it's written on the amp exactly which ports to use, I've seen rt+ and left-, I've seen rt+ and left+ and also rt- and left+. All depends on the amp itself.