You need 9-12W of LED without lens base on my experience in design the Edge Savior.
Even for medium plants? That seems high to me.
BTW, replacement base idea is great even though it does take some of the visual area of the Edge. How much they charge you?
I called Hagen directly. The number for the U.S. office is 1-800-724-2436. Since the base is technically not a replacement part and you cannot buy on their website or any other, they simply asked me for my color of my edge (pewter), what model (6.6g LED) and my address. The "replacement" arrived in 3 days and I paid nothing for it, not even shipping. Their customer service has always been wonderful, part of my reason I love Hagen/Fluval.