As for Amazon Sword plants I read that 2 watts per gallon would be best for them. That a bit high compared to the generic low lights that come with tank kits or even just the bulbs that come with the light itself.
Most Swords are not low light plants, just like Ken mentioned. There are a couple that do ok in lower light but they stay pretty small & still need more light than comes in the average aquarium kit. Ambulia is great for a background plant in a low light tank & Hygrophila Polysperma 'Sunset' can work well depending on exactly how much light you have. The Hygro do well in the higher end of the low light range. Elodea is fantastic for low light tanks.
I've sworn off of hornwort forever. I can never keep it looking good and it ends up shedding leaves and making a mess of the tank.
Ken's suggestion for anubias is a good one. There are plenty of varieties that grow to a foot tall or more. Lanceolata, hastifolia, congensis all come to mind. If you like the look of a sword plant but you don't really have enough light for one, try a larger anubias for a similar effect.
You may be able to grow vallisneria as a background plant. I'd consider it to be on the high end of low light.