I recently had a powered subwoofer installed on my EV9 last week. The stock Meridian subwoofer is hot garbage and I was really looking for a solution that provided enough power without sacrificing cargo space. I ended up purchasing a JL Audio Microsub+ 8 (dimensions: 18-1/2"W x 11-1/8"H x 5-1/8"D) and I’ve been really happy with it. Don’t let the 8” subwoofer fool you, this thing can pound if you want it to. I keep it at the lowest setting. I purchased the powered sub on my own from Abt. The cost to install including labor and cables was $440. This is a great solution, but it wasn’t cheap. I could’ve gone with a different powered sub, but JL Audio ia the highest quality. Below are some pics with a couple ways you can position the box.